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Welcome to Microbiology Department!Welcome to Microbiology Department!

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Medical MicrobiologyMedical Microbiology

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DefinitionDefinition

Microbiology: the science that studyMicrobiology: the science that study

microorganismsmicroorganisms

Microorganisms: single cell organisms that canMicroorganisms: single cell organisms that can be seen using light or electronic microscope be seen using light or electronic microscope

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Microbiology: the science that studyMicrobiology: the science that studymicroorganismsmicroorganisms

Micro – mic Micro – mic (small)(small)

Bios – Bios – life.life. Why we looking them?Why we looking them? They have some “goodThey have some “good

parts” (will try to use in the human benefit) and parts” (will try to use in the human benefit) and

“bad” (will try to eliminate them).“bad” (will try to eliminate them).

Microorganisms: single cell organisms that can beMicroorganisms: single cell organisms that can be

seen using light or electronic microscopeseen using light or electronic microscope

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Main categoriesMain categories

Cellular microorganismsCellular microorganisms::

- eukaryotic cellseukaryotic cells (fungi and protoooa) !" #(fungi and protoooa) !" #

true$ %&'* # nucleustrue$ %&'* # nucleus- prokaryotic cells prokaryotic cells: bacteria and blue +green: bacteria and blue +green

algae (,' # before before nucleus).algae (,' # before before nucleus).

VirusesViruses: are strict intracellular infective: are strict intracellular infective particle (need viable cell to replicate)$ they are particle (need viable cell to replicate)$ they are

simplest than a cell (see /irology module)simplest than a cell (see /irology module)

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HistoryHistory

Robert HookeRobert Hooke published 0Micrographia0 in 1223. published 0Micrographia0 in 1223.

t is his most famous wor4 and is notable for thet is his most famous wor4 and is notable for the

stunning illustrations drawn by 5oo4e himself.stunning illustrations drawn by 5oo4e himself.

The picture of theThe picture of the fleaflea shown above is one of hisshown above is one of his

most famous images$ the original is 16 inches across.most famous images$ the original is 16 inches across.

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ntonius an "eeuwenhoek ntonius an "eeuwenhoek

#ather of microbiology#ather of microbiology

ntonius an "eeuenhoek ntonius an "eeuenhoek was a 7utchwas a 7utch

businessman who became an e8pert lens businessman who became an e8pert lens

grinder and amateur scientist.grinder and amateur scientist.

9ith a self-built microscope he investigated9ith a self-built microscope he investigated

various liuids tissues and minerals andvarious liuids tissues and minerals and

corresponded about his discoveries with thecorresponded about his discoveries with the

scientific authorities of his time.scientific authorities of his time.

;etter sent to 'oyal &cademy (1<12);etter sent to 'oyal &cademy (1<12)

http://worldcat.org/search?q=no:034323518

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HistoryHistory

"ouis $asteur"ouis $asteur

5e was a =rench chemist and5e was a =rench chemist and

microbiologist.microbiologist. 5e is best 4nown for his remar4able5e is best 4nown for his remar4able

brea4throughs in the causes and preventions of brea4throughs in the causes and preventions ofdisease.disease.

5is discoveries reduced mortality from puerperal5is discoveries reduced mortality from puerperalfever and he created the first vafever and he created the first vacccine for rabies.cine for rabies.

5is e8periments supported the5is e8periments supported the germ theory of germ theory of

disease.disease.

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5e was best 4nown to the general public for5e was best 4nown to the general public forinventing a method to stop mil4 and wine frominventing a method to stop mil4 and wine fromcausing sic4ness a process that came to becausing sic4ness a process that came to be

calledcalled pasteurization. pasteurization. 5e is regarded as one of the three main5e is regarded as one of the three main

founders of microbiology together withfounders of microbiology together with

=erdinand >ohn and 'obert %och.=erdinand >ohn and 'obert %och.

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Robert %ochRobert %och

and his postulatesand his postulates That the organism could be discoverableThat the organism could be discoverable

in every instance of the disease$in every instance of the disease$

thethe microorganisms can be isolated from the lesionsmicroorganisms can be isolated from the lesions . .

That e8tracted from the body the germ could beThat e8tracted from the body the germ could be produced in a produced in a pure culture pure culture&& maintainable over severalmaintainable over severalmicrobial generations.microbial generations.

That theThat the disease could be reproduceddisease could be reproduced in e8perimentalin e8perimental

animals through a pure culture removed by numerousanimals through a pure culture removed by numerousgenerations from the organisms initially isolated$ thatgenerations from the organisms initially isolated$ thatthe organism could he retrieved from the inoculatedthe organism could he retrieved from the inoculatedanimal and cultured anewanimal and cultured anew....

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&lthough some pathogenic entities notably viruses&lthough some pathogenic entities notably viruseshad to be accepted without meeting all the conditionshad to be accepted without meeting all the conditionsmost conditions were able to be fulfilled.most conditions were able to be fulfilled.

The applicability and thin4ing behind these rigorousThe applicability and thin4ing behind these rigorous postulates boosted the dogma of postulates boosted the dogma of specific aetiologyspecific aetiology --the idea that athe idea that a disease has a specific causatie agentdisease has a specific causatie agent ..

The implication was that once the agent has beenThe implication was that once the agent has been

isolated it will be possible to control the disease.isolated it will be possible to control the disease... %och announced that he had isolated and grown the%och announced that he had isolated and grown the

tubercle bacillus to the ,hysiological ?ociety oftubercle bacillus to the ,hysiological ?ociety of

@erlin on March 166A. 5e believed this to be the@erlin on March 166A. 5e believed this to be thecause of all forms of tuberculosis.cause of all forms of tuberculosis. n 1BC3 %och won the *obel ,rie for ,hysiology orn 1BC3 %och won the *obel ,rie for ,hysiology or

MedicineMedicine " " For his investigation and discoveries inFor his investigation and discoveries inrelation to tuberculosisrelation to tuberculosis" " ..

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Disciplines of MicrobiologyDisciplines of Microbiology

Microbiology hasMicrobiology has manymany different disciplines or subdifferent disciplines or sub

disciplines (as it were) beneath it.disciplines (as it were) beneath it.

ncluded in these and worth special mention asncluded in these and worth special mention as

they will be the only maDor disciplines furtherthey will be the only maDor disciplines furtherdiscussed within thisdiscussed within this courscours are are::

- virologyvirology

- genetics (i.e.genetics (i.e. 7*&7*&))- bacteriology and bacteriology and

- parasitology. parasitology.

http://dna.micrbobioloygguide.com/



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- &lso included within the general discipline of&lso included within the general discipline of

microbiology are:microbiology are:

Microbial ,hysiology Microbial Eenetics >ellularMicrobial ,hysiology Microbial Eenetics >ellular

MicrobiologyMicrobiology Medical Microbiology Medical Microbiology /eterinary /eterinary

Microbology !nvironmental MicrobologyMicrobology !nvironmental Microbology

!volutionary Microbiology ndustrial!volutionary Microbiology ndustrial

Microbology &ero Microbology =oodMicrobology &ero Microbology =oodMicrobology andMicrobology and ,,harmaceutical microbology.harmaceutical microbology.

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The fields listed above encompass vaccinaThe fields listed above encompass vaccina--

tions nuttions nutr r ition se8ual procreation cellularition se8ual procreation cellular

healthhealth etc. etc.

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MicrobiologyMicrobiology

'acteria structures and functions'acteria structures and functions

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'acteria'acteria are living forms that areare living forms that are

microscopical in sie (1-1Cmicroscopical in sie (1-1C µµm) and relativelym) and relatively

simple unicellular in structuresimple unicellular in structure

a microscope is therefore necessary for theira microscope is therefore necessary for their

observation.observation.

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(tructure(tructure

!ach cell consists of a!ach cell consists of a body of protoplasm&body of protoplasm&

thethe protoplast protoplast enclosed by a thin enclosed by a thin

semipermeable membranesemipermeable membrane the the cytoplasmiccytoplasmic

membranemembrane and also in most cases by anand also in most cases by an

outer relatively rigidouter relatively rigid cell wallcell wall..

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)he bacterial structures may be diided into)he bacterial structures may be diided into

three categories*three categories*

1.1. +ssential structures+ssential structures present in all bacteria present in all bacteria

A.A. (tructures(tructures present in present in some speciessome species (primary(primary

ta8onomic characters) +ta8onomic characters) + see ta8onomysee ta8onomy

F.F. (tructures(tructures present in present in some strainssome strains of someof some

speciesspecies

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+ssential structures& present in all+ssential structures& present in all

bacteriabacteria

,rotoplast with:,rotoplast with:

-

cytoplasmcytoplasm- nuclear bodynuclear body (is lac4s nucleolus)(is lac4s nucleolus)

>ytoplasmic membrane>ytoplasmic membrane

>ell wall>ell wall

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'acteria,structure'acteria,structure

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)a-onomy)a-onomy . using constant . using constant

structures for classification in*structures for classification in*

/rder/rder

Family Family

EenusEenus

?pecies?pecies

?trains?trains

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01 (tructures present in some species01 (tructures present in some species

2primary ta-onomic characters3*2primary ta-onomic characters3*

flagella$flagella$

spores$spores$ inclusion granules.inclusion granules.

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#lagellum#lagellum

4 ( i i f

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41 (tructures present in some strains of41 (tructures present in some strains of

some species*some species* are not useful forare not useful for

ta-onomyta-onomy

fimbriae (common pili)fimbriae (common pili)

se8 pili$se8 pili$ glicocali8 (capsule microcapsule looseglicocali8 (capsule microcapsule loose

slime).slime).

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#imbriae 2pili3& se- pili& capsule#imbriae 2pili3& se- pili& capsule

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bacteriabacteria

$rotoplast$rotoplast with:with:

-

cytoplasmcytoplasm- nuclear bodynuclear body


>ell wall>ell wall

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(tructure(tructure

TheThe protoplast protoplast is differentiated into a maDoris differentiated into a maDor

part the part the cytoplasmcytoplasm and and

an inner body thean inner body the nuclear bodynuclear body which which

contains the hereditary determinants ofcontains the hereditary determinants of

character thecharacter the genes genes borne on borne on chromosomechromosome..

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(chematic presentation(chematic presentation

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'acteria'acteria ## prokaryotic cellsprokaryotic cells

)he bacteria are prokaryotic cells1)he bacteria are prokaryotic cells1

t is useful to draw a clear distinction betweent is useful to draw a clear distinction between

relatively primitive (relatively primitive ( prokaryotic prokaryotic) and more) and more

advanced (advanced (eukaryoticeukaryotic) cells) cells (see >ell biology(see >ell biology

too)too)..

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)h i di ti i hi f t f th)h i di ti i hi f t f th

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)he main distinguishing features of the)he main distinguishing features of the

prokaryotic cell are*prokaryotic cell are*

tsts nucleusnucleus appears as a simple homogeneousappears as a simple homogeneous

body containing body containing a single chromosomea single chromosome notnot

possessing a nuclear membrane separating it possessing a nuclear membrane separating it

from the cytoplasm nofrom the cytoplasm nott a nucleolus noa nucleolus nott aa

spindle nospindle nott a number of separate non-identicala number of separate non-identical

chromosomes.chromosomes.

5t reproduces by binary fission&5t reproduces by binary fission& not bynot bymitotic division.mitotic division.

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6ucleus 7 D66ucleus 7 D6

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prokaryotic cellprokaryotic cell

5t lacks the internal membranes5t lacks the internal membranes isolating theisolating therespiratory and photosynthetic enymerespiratory and photosynthetic enymesystems in specific organelles.systems in specific organelles.

Thus theThus the respiratory enzymesrespiratory enzymes in bacteria arein bacteria arelocated mainly in thelocated mainly in the peripheral cytoplasmic peripheral cytoplasmic

membrane.membrane.

The cytoplasm is a soft gel and has no internalThe cytoplasm is a soft gel and has no internalmobility.mobility.

,ro4aryotes have <C ?vedberg unit ribosomes.,ro4aryotes have <C ?vedberg unit ribosomes.

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prokaryotic cellprokaryotic cell

ts rigid cell wall contains as its maints rigid cell wall contains as its main

strengtheningstrengthening element a specific peptidoglycanelement a specific peptidoglycan

(substance not found in eu4aryotic organisms).(substance not found in eu4aryotic organisms).

?teroids are absent in the procaryotic cell wall?teroids are absent in the procaryotic cell wall

(e8ception mycoplasmas).(e8ception mycoplasmas).

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$R/%R8/)5C C+"" ()R9C)9R+$R/%R8/)5C C+"" ()R9C)9R+

TheThe protoplast protoplast is bounded peripherally by ais bounded peripherally by a

very thin elastic and semipermeablevery thin elastic and semipermeable

cytoplasmic membranecytoplasmic membrane..

utside and closely covering this lies theutside and closely covering this lies the

rigid supportingrigid supporting cell wall cell wall which is porous and which is porous and

relatively permeable.relatively permeable.

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Cell membrane and cell wallCell membrane and cell wall

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:1 +ssential structures& present in all:1 +ssential structures& present in all

bacteriabacteria

thethe cytoplasmcytoplasm containing ribosomescontaining ribosomes andand

nuclear bodynuclear body$$

thethe cytoplasmic membrane 2cytoplasmic membrane 2oror plasmaplasma

membrane3membrane3$$

thethe rigid cell wallrigid cell wall (e8ception mycoplasmas).(e8ception mycoplasmas).

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=lagella$=lagella$

?? pores$ pores$ nclusion granules.nclusion granules.

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2not primary ta-onomic characters3*2not primary ta-onomic characters3*

- >ommon pilli and se8 pilli- >ommon pilli and se8 pilli

- >apsule (glycocali8)- >apsule (glycocali8)

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#lagella 2electron microscopy3#lagella 2electron microscopy3

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(pores(pores ((ClostridiumClostridium spp.)spp.)

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5nclusions granules5nclusions granules

(starch glycogen polyphosphate etc.)(starch glycogen polyphosphate etc.)

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bacteriabacteria

$rotoplast$rotoplast with:with:

-

cytoplasmcytoplasm- nuclear bodynuclear body


>ell wall>ell wall

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'acterial nuclear body 2D63'acterial nuclear body 2D63

&> & &

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@&>T!'&; 7*&@&>T!'&; 7*&

TheThe bacterial cell lacks a nuclear membrane;bacterial cell lacks a nuclear membrane;

instead the 7*& is concentrated in theinstead the 7*& is concentrated in the

cytoplasm as acytoplasm as a nuclear bodynuclear body11

The nuclear body consists of aThe nuclear body consists of a singlesingle

chromosomechromosome (1 mm(1 mm to A mmto A mm length) oflength) of

double-stranded circular covalently closeddouble-stranded circular covalently closed

super-coiled 7*&.super-coiled 7*&.

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(i;e(i;e

The cell solves the problem of pac4aging thisThe cell solves the problem of pac4aging this

enormous 7*& molecule (A-F 8 1Cenormous 7*& molecule (A-F 8 1CBB 47a) by47a) by

condensing and looping it into the supercoiledcondensing and looping it into the supercoiled

state.state.

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D6 molecule and plasmidD6 molecule and plasmid

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$lasmids$lasmids

n many bacteria a small portion of 7*&n many bacteria a small portion of 7*&

persists as persists as e-trachromosomal elementse-trachromosomal elements

referred to asreferred to as plasmid plasmid ss which are also which are also

circular but are much smaller than bacterialcircular but are much smaller than bacterialchromosomes.chromosomes.

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$lasmids, functions$lasmids, functions

,lasmids encode variable numbers of genes,lasmids encode variable numbers of genes

(mainly responsible for the bacterial survival(mainly responsible for the bacterial survival

in the environment) and often determinein the environment) and often determine

irulent behaiorirulent behaior oror antibiotic resistanceantibiotic resistance..

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<&:=<&:=

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6uclear body6uclear body

The nuclear body isThe nuclear body is constantly presentconstantly present in allin all

cells and under all conditions of culture.cells and under all conditions of culture.

tt replicatesreplicates by by growthgrowth andand simple fission&simple fission&

andand not by mitosis.not by mitosis. !lectron micrographs reveal the!lectron micrographs reveal the

absence of the outer nuclear membrane separating it from theabsence of the outer nuclear membrane separating it from thecytoplasm and of the nucleolus.cytoplasm and of the nucleolus.

@acterial 7*& has a similar structure to that of@acterial 7*& has a similar structure to that of

eu4aryotic chromatin (seeeu4aryotic chromatin (see EEenetic).enetic).

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6uclear body,s obseration6uclear body,s obseration

The nuclear body canGt be seen with the lightThe nuclear body canGt be seen with the light

microscope in bacteria stained by usualmicroscope in bacteria stained by usual

methods because it is covered by the multitudemethods because it is covered by the multitude

of '*& molecules from the bacterialof '*& molecules from the bacterialcytoplasm$cytoplasm$

it is observed on stained films after '*&it is observed on stained films after '*&

hydrolysis.hydrolysis.

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#unctions#unctions

The bacterial 7*&The bacterial 7*& stores the geneticstores the genetic

information1information1

t is involved int is involved in autoreplicationautoreplication (by which(by which

copies of genetic information are transmittedcopies of genetic information are transmitted

to daughter cells) andto daughter cells) and

heteroreplicationheteroreplication (by which the information is(by which the information is

copied in m'*& seuences).copied in m'*& seuences).

ReplicationReplication

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ReplicationReplication

(relation of bacteriaGs structure and antibiotics)(relation of bacteriaGs structure and antibiotics)

+ ti l t t t i ll+ ti l t t t i ll

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bacteriabacteria

,rotoplast,rotoplast with:with:

-

cytoplasmcytoplasm

- nuclear bodynuclear body


>ell wall>ell wall

>HT,;&?M = @&>T!'&>HT,;&?M = @&>T!'&

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>HT,;&?M = @&>T!'&>HT,;&?M = @&>T!'&

The cytoplasm of bacteria is aThe cytoplasm of bacteria is a iscous wateryiscous watery

solution&solution& oror soft gelsoft gel containing a variety of organic containing a variety of organicand inorganic solutes and numerous small granulesand inorganic solutes and numerous small granulescalledcalled ribosomesribosomes..

The variety of organelles seen in eu4aryotic cells isThe variety of organelles seen in eu4aryotic cells ismissing in bacteria because the cytoplasmicmissing in bacteria because the cytoplasmicmembrane performs many comple8 functions carriedmembrane performs many comple8 functions carriedout by these organelles.out by these organelles.

The cytoplasm of bacteria also differs from that of theThe cytoplasm of bacteria also differs from that of theeu4aryotic organisms in not showing signs of internaleu4aryotic organisms in not showing signs of internalmobility.mobility.

'@?M!?'@?M!?

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'@?M!?'@?M!?

Ribosomes are comple- globular structuresRibosomes are comple- globular structures

composed ofcomposed of seeral R6 moleculesseeral R6 molecules and manyand many

associatedassociated proteins>proteins> they function as thethey function as the actieactie

centers for protein synthesiscenters for protein synthesis.. @acterial ribosomes are slightly smaller (1C-AC nm)@acterial ribosomes are slightly smaller (1C-AC nm)

than those of eu4aryotic cells and they have athan those of eu4aryotic cells and they have a

sedimentation constant ofsedimentation constant of <=(<=( (?vedberg units) being(?vedberg units) being

composed of acomposed of a 4=(4=( (1 '*& molecule and A1 proteins(1 '*& molecule and A1 proteins?1-?A1) and a?1-?A1) and a =( subunit=( subunit (A '*& molecules and FI(A '*& molecules and FI

proteins ;1-;FI). proteins ;1-;FI). @oth can be target for antibiotics.@oth can be target for antibiotics.

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RibosomesRibosomes

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RibosomesRibosomes

They may be seen with the electronThey may be seen with the electron

microscope in number apro8. AC.CCC per cell.microscope in number apro8. AC.CCC per cell.

They are strung together on strands ofThey are strung together on strands of

messenger '*& (m'*&) to formmessenger '*& (m'*&) to form polysomes polysomes

and it is at this siteand it is at this site wherewhere the code of thethe code of the

m'*& is translated into peptide seuences.m'*& is translated into peptide seuences.

'ibosoms descovery by romanian scientist'ibosoms descovery by romanian scientist

Eeorge !mil ,alade (*obel price)Eeorge !mil ,alade (*obel price)


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=lagella$=lagella$

?? pores$ pores$

nclusion granules.nclusion granules.

*>;"?* E'&*";!?*>;"?* E'&*";!?

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*>;"?* E'&*";!?*>;"?* E'&*";!?

n many species of bacterian many species of bacteria round granulesround granules

are observed in the cytoplasm.are observed in the cytoplasm.

These are not permanent or essentialThese are not permanent or essential

structures and may be absent under certainstructures and may be absent under certain

conditions of growth.conditions of growth.

They appear to be aggregates of substancesThey appear to be aggregates of substances

concerned with cell metabolism e.g. an e8cessconcerned with cell metabolism e.g. an e8cess

metabolite stored as ametabolite stored as a nutrient reserenutrient resere..

*>;"?* E'&*";!?*>;"?* E'&*";!?

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*>;"?* E'&*";!?*>;"?* E'&*";!?(starch glycogen(starch glycogensulphur polyphosphatesulphur polyphosphate etc.)etc.)

*>;"?* E'&*";!?*>;"?* E'&*";!?

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*>;"?* E'&*";!?*>;"?* E'&*";!?

(e8emples functions)(e8emples functions)

They consist ofThey consist of olutinolutin (polyphosphate)(polyphosphate) lipidlipidglycogen& starchglycogen& starch or or sulfursulfur..

Their demonstration may assist in theTheir demonstration may assist in the identificaidentifica77

tiontion of certain organisms (of certain organisms (primary ta-onomicprimary ta-onomiccharactercharacter)$)$

!8.: the!8.: the diphtheria bacillusdiphtheria bacillus ((CorynebacteriumCorynebacterium

diphteriaediphteriae) may be distinguished from related) may be distinguished from related bacilli found in the throat by its content of bacilli found in the throat by its content ofolutinolutin granules.granules.

Corynebacterium diphteriaeCorynebacterium diphteriae

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Corynebacterium diphteriaeCorynebacterium diphteriae

(volutine granules - dar4)(volutine granules - dar4)

+ssential structures present in all+ssential structures present in all

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bacteriabacteria

,rotoplast with:,rotoplast with:

- cytoplasmcytoplasm


Cytoplasmic membraneCytoplasmic membrane

>ell wall>ell wall

>HT,;&?M> M!M@'&*!>HT,;&?M> M!M@'&*!

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>HT,;&?M> M!M@'&*!>HT,;&?M> M!M@'&*!

The cytoplasmic membrane isThe cytoplasmic membrane is the physicalthe physical andand

metabolic barriermetabolic barrier between the interior and between the interior and

e8terior of the bacterial cell.e8terior of the bacterial cell.

t is 3-1C nm thic4 consists mainly oft is 3-1C nm thic4 consists mainly of lipoproteinlipoprotein

and is visible in some ultrathin sections e8aminedand is visible in some ultrathin sections e8amined

with the electron microscope (!M).with the electron microscope (!M).

>ell (>ytoplasmic) Membrane

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=le8ible phospholipid bilayer sheet

5ydrophobic tails

5ydro phillic heads

May contain steroid- li4e molecules:

hopanoids to stabilie structure.


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The lipidThe lipid

molecules aremolecules arearranged in aarranged in a

double layerdouble layer

with theirwith their

hydrophilichydrophilic

polar regions polar regions

e8ternallye8ternally

aligned and inaligned and in

contact with acontact with a

layer of proteinlayer of proteinat each surface.at each surface.

>ytoplasmic membrane

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>ytoplasmic membrane

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Cytoplasmic membraneCytoplasmic membrane


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@oundary between a cell and its environment

7ynamic interface

>hanges with temperature age environment

M!??M!?M!??M!?

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M!??M!?M!??M!?

They areThey are conolutedconoluted oror multilaminated memmultilaminated mem77

branousbranous bodies visible in electron microscope. bodies visible in electron microscope. They develop by comple8They develop by comple8 inaginationinagination of theof the

cytoplasmic membranecytoplasmic membrane into the cytoplasminto the cytoplasmsometimes in relation to the nuclear body and oftensometimes in relation to the nuclear body and oftenfrom the sites of cross-wall formation during cellfrom the sites of cross-wall formation during celldivision.division.

Mesosomes are thought to be involved in theMesosomes are thought to be involved in themechanisms responsible for the compartmenting ofmechanisms responsible for the compartmenting ofD6 at cell diisionD6 at cell diision andand sporulation1sporulation1

M!??M!?M!??M!?

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M!??M!?M!??M!?

#unctions of the pro#unctions of the prokkaryotic plasmaaryotic plasma

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#unctions of the pro#unctions of the prok k aryotic plasmaaryotic plasma

membranemembrane

/smotic or permeability/smotic or permeability barrierbarrier (s(separate “outside”from “inside”).

;ocation of;ocation of transport systemstransport systems for specific solutesfor specific solutes(nutrients and ions)(nutrients and ions)..

Mesosomes are thought to be involved in theMesosomes are thought to be involved in the

mechanisms responsible for the compartmenting ofmechanisms responsible for the compartmenting of- D6 at cell diisionD6 at cell diision andand- sporulationsporulation

#unctions of the pro#unctions of the prokkaryoticaryotic

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#unctions of the pro#unctions of the prok k aryoticaryotic

plasma membraneplasma membrane

+nergy generating functions+nergy generating functions involving involvingrespiratory and photosynthetic electronrespiratory and photosynthetic electrontransport systems establishment of protontransport systems establishment of proton

motive force and transmembranous &T,-motive force and transmembranous &T,-synthesiing &T,asesynthesiing &T,ase..

(ynthesis(ynthesis ofof membrane lipidsmembrane lipids (including(includinglipopolysaccharide in Eram-negative cells)lipopolysaccharide in Eram-negative cells)..

#unctions of the pro#unctions of the prokkaryotic plasmaaryotic plasma

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#unctions of the pro#unctions of the prok k aryotic plasmaaryotic plasma

membranemembrane

(ynthesis(ynthesis ofof mureinmurein (cell wall peptidoglycan)(cell wall peptidoglycan).. ssembly and secretion of e-tracytoplasmicssembly and secretion of e-tracytoplasmic

proteinsproteins..

Coordination of D6 replicationCoordination of D6 replication andandsegregation with septum formation and cellsegregation with septum formation and celldivisiondivision..

Chemota-isChemota-is (both motility(both motility per se per se and sensingand sensingfunctions)functions).. "ocation of speciali;ed en;yme system"ocation of speciali;ed en;yme system11

+ssential structures present in all+ssential structures& present in all

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bacteriabacteria

,rotoplast,rotoplast with:with:- cytoplasmcytoplasm



Cell wallCell wall

C+"" W""C+"" W""

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C+"" W""C+"" W""

TheThe cell wall encases protoplast cell wall encases protoplast and lies immediatelyand lies immediatelye8ternal to the cytoplasmic membrane.e8ternal to the cytoplasmic membrane.

t is 1C-A3 nmt is 1C-A3 nm thick& strongthick& strong andand rigidrigid..

t supports the wea4 cytoplasmic membrane againstt supports the wea4 cytoplasmic membrane againstthethe high internal osmotic pressurehigh internal osmotic pressure (3 + AC atms) of(3 + AC atms) ofthe protoplasm and maintains thethe protoplasm and maintains the characteristiccharacteristic

shapeshape of the bacterium in its coccal bacillaryof the bacterium in its coccal bacillaryfilamentous or spiral form.filamentous or spiral form.

TheThe rigid cell wall is entirely absent in a fewrigid cell wall is entirely absent in a few

unusual bacteriaunusual bacteria (e.g. mycoplasmas genus(e.g. mycoplasmas genus Mycoplasma Mycoplasma).).

' i , h @' t i , h @ t

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'acteria,s shapes@arrangement'acteria,s shapes@arrangement

C+"" W""C+"" W""

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C+"" W""C+"" W""

TheThe integrityintegrity of the cell wall is essential to theof the cell wall is essential to the

viabilityviability of the bacterium.of the bacterium.

f the wall is wea4ened or rupturedf the wall is wea4ened or ruptured (as anti-(as anti-

biotics target) biotics target) the protoplasm may swell from the protoplasm may swell from

osmotic inflow of water and burst the wea4osmotic inflow of water and burst the wea4

cytoplasmic membrane (lysis).cytoplasmic membrane (lysis).

'acterial rigid cell wall is made up of peptidoglycan'acterial rigid cell wall is made up of peptidoglycan

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'acterial rigid cell wall is made up of peptidoglycan'acterial rigid cell wall is made up of peptidoglycan

and special structuresand special structures

Peptidoglycan Peptidoglycan 22mureinmurein33 is the principalis the principal

structural component of the cell wall.structural component of the cell wall.

This compoundThis compound is found in bothis found in both Eram-positiveEram-positive

and Eram-negative bacteria although isand Eram-negative bacteria although is moremore

abundant in Grampositive organismsabundant in Grampositive organisms..

$ id li f A i i b i$ tid li f A iti b t i

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$eptidoglican of Aram positie bacteria$eptidoglican of Aram positie bacteria

$ id li f A i b i$ tid li f A ti b t i

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$eptidoglican of Aram negatie bacteria$eptidoglican of Aram negatie bacteria

Aram 2B3& 273 and acid fast bacterialAram 2B3& 273 and acid fast bacterial

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A a 2 3& 2 3 a d ac d ast bacte a2 3& 2 3

cell wall 2comparison3cell wall 2comparison3

Aram 2B3 and Aram 273 bacterial cellAram 2B3 and Aram 273 bacterial cell

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2 3 2 32 3 2 3

wall 2comparison3wall 2comparison3

$ tid l$ tid l

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$eptidoglycan$eptidoglycan

,eptidoglycan polymers consist of repeating,eptidoglycan polymers consist of repeating

dissacharidesdissacharides formed by:formed by:

- 67acetyl7glucosamine67acetyl7glucosamine (*&E) and(*&E) and

- 67acetylmuramic acid67acetylmuramic acid (*&M).(*&M).

$ tid l$ tid l

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The *-acetylmuramic (*&M) acid lin4s theThe *-acetylmuramic (*&M) acid lin4s the

dissacharides to andissacharides to an oligopeptide chainoligopeptide chain

consisting of four aminoacidsconsisting of four aminoacids (usually ;-alanine(usually ;-alanine

7-glutamic acid either meso-diaminopimelic acid + in Eram-7-glutamic acid either meso-diaminopimelic acid + in Eram-negative bacteria + or ;-lysine + in Eram-positive bacteria andnegative bacteria + or ;-lysine + in Eram-positive bacteria and

7-alanine).7-alanine).

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$ tid l$eptidogl can

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"yso;yme"yso;yme hydrolyses peptidoglycan byhydrolyses peptidoglycan by

cleaving the glycosil bonds between *-acetyl-cleaving the glycosil bonds between *-acetyl-

muramic acid and the *-acetylglucosamine.muramic acid and the *-acetylglucosamine.

C ll di i iCell diision

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Cell diisionCell diision

>ell division occurs by the development from>ell division occurs by the development fromthe periphery inwards of a transversethe periphery inwards of a transverse cytocyto

plasmic membrane plasmic membrane and aand a transverse cell transverse cell wall wall

oror cross wall cross wall .. The cell wall plays an important part in cellThe cell wall plays an important part in cell

division.division. &s the protoplast increases in mass the cell&s the protoplast increases in mass the cell

wall is elongated by the intercalation of newlywall is elongated by the intercalation of newlysynthesied subunits into the various wallsynthesied subunits into the various walllayers.layers.

Di i i f llDiision of cell

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Diision of cellDiision of cell

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Cell wallCell wall

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Cell wallCell wall

TheThe cell wallcell wall can be demonstrated by specialcan be demonstrated by special

staining methodsstaining methods but most clearly by but most clearly by

electron microscope.electron microscope.

!t is not seen in conventionally stained !t is not seen in conventionally stainedsmearssmears e8amined with the light microscopee8amined with the light microscope

but its chemical structure is responsible for the but its chemical structure is responsible for the

staining of bacteria in differential stainings.staining of bacteria in differential stainings.

Cell wallCell wall

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Cell wallCell wall

Aram stainingAram staining divides bacteria in gram-divides bacteria in gram-

positive ( positive (violetviolet) and gram-negative () and gram-negative (redred)$)$

"iehl#eelsen staining "iehl#eelsen staining divides bacteria individes bacteria in

acid-fast (acid-fast (redred) and non-acid-fast () and non-acid-fast ( blue blue).).

Aram stainingAram staining

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Aram7stainingAram7staining

Eram-staining the most common criterion forEram-staining the most common criterion forgrouping medically important bacteria is a simplegrouping medically important bacteria is a simpledifferential staining techniue that employsdifferential staining techniue that employs crystalcrystalviolet violet (an aniline dye) as the primary stain and(an aniline dye) as the primary stain and fuchsin fuchsin

(a red dye) as a counter-stain.(a red dye) as a counter-stain. Eram-positive bacteria appear violet because theyEram-positive bacteria appear violet because they

retain the crystal violet and resist alcohol decoloration.retain the crystal violet and resist alcohol decoloration. Eram-negative bacteria appear red because they areEram-negative bacteria appear red because they are

decoloried completely by ethanol and they ta4e updecoloried completely by ethanol and they ta4e upfuchsin the counter-stain.fuchsin the counter-stain.

Aram stainingAram staining

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g

it is influenced by cell wall structureit is influenced by cell wall structure

$taphylococcus $taphylococcus%Gram positive cocci arranged in%Gram positive cocci arranged in

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%Gram positive cocci arranged in%Gram positive cocci arranged in

clusters&clusters&

Gram negative bacilliGram negative bacilli

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Gram negative bacilli Gram negative bacilli

'cid fast bacilli 'cid fast bacilli (red)(red)inin "iehl #eelsen staining"iehl #eelsen staining

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inin "iehl ( #eelsen staining "iehl ( #eelsen staining

%e). Mycobacterium tuberculosis&%e). Mycobacterium tuberculosis&

Eram positive bacteriaEram positive bacteria

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Eram-positive bacteriaEram-positive bacteria

Aram7positieAram7positie bacteriabacteria have a simpler buthave a simpler butthic4er cell wall consisting primarily ofthic4er cell wall consisting primarily of tri7tri7

dimensional peptidoglycandimensional peptidoglycan withwith teichoicteichoic

acid acid polymerspolymers (ribitol or glycerol phosphate(ribitol or glycerol phosphatecomple8ed with sugar residues) dispersedcomple8ed with sugar residues) dispersed

throughout$throughout$

some of this material (some of this material (lipoteichoic acid lipoteichoic acid ) is) islin4ed to lipids buried in the cell membrane.lin4ed to lipids buried in the cell membrane.

Eram positive bacteriaEram positive bacteria

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)eichoic acids)eichoic acids

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)eichoic acids)eichoic acids

The teichoic acids are maDor surfaceThe teichoic acids are maDor surface antigens 2seeantigens 2seeimmunology3immunology3 in the Eram-positive species thatin the Eram-positive species that

possess them. possess them.

They bind magnesium ion and play a role in theThey bind magnesium ion and play a role in thefunction of thefunction of the cytoplasmic membrane,s en;ymescytoplasmic membrane,s en;ymes..

They bind autolytic enymes being thus involved inThey bind autolytic enymes being thus involved in

the cellGsthe cellGs growthgrowth andand diisiondiision..

They areThey are receptors for bacteriophagesreceptors for bacteriophages (viruses of(viruses of

bacteria). bacteria).

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J $olysacharides$olysacharides (eg. ;ancefield antigens + streptococci)(eg. ;ancefield antigens + streptococci)

J (urfaces proteins that act as*(urfaces proteins that act as*- adhesinesadhesines

- antiphagocytic structuresantiphagocytic structures ((M proteinM protein (S. pyogenes!(S. pyogenes! &&

protein protein (S. aureus!(S. aureus! binding proteins to fibronectine etc binding proteins to fibronectine etc).).

Eram positive bacteriaEram-positive bacteria

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Eram-negative bacteriaEram-negative bacteria

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Eram-negative bacteriaEram-negative bacteria

Aram7negatieAram7negatie bacteriabacteria have a cell wall thathave a cell wall thatis thinner than that of Eram-positive bacteriais thinner than that of Eram-positive bacteria

withwith bi7dimensional peptidoglycan and nobi7dimensional peptidoglycan and no

teichoic acidsteichoic acids.. &n additional membrane the&n additional membrane the outer membraneouter membrane

lies above the peptidoglycan layer.lies above the peptidoglycan layer.

The outer membrane is much thic4er than theThe outer membrane is much thic4er than thesingle peptidoglycan layer.single peptidoglycan layer.

)he outer membrane)he outer membrane

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The outer membrane is composed of:The outer membrane is composed of:- aa bilipid layer bilipid layer &&

-

proteins proteins andand- lipopolysaccharidelipopolysaccharide 2"$(2"$( or or endoto-inendoto-in).).

7iagrams of the cell wall structure of Eram-negative7iagrams of the cell wall structure of Eram-negative

(left) and Eram-positive bacteria.(left) and Eram-positive bacteria.

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%ey: peptidoglycan layer (yellow)$ protein (purple)$%ey: peptidoglycan layer (yellow)$ protein (purple)$

teichoic acid (green)$ phospholipid (brown)$teichoic acid (green)$ phospholipid (brown)$

lipopolysaccharide (orange).lipopolysaccharide (orange).


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Cell wall of Aram 273 bacteriaCell wall of Aram 273 bacteria

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Cell wall of Aram 273 bacteriaCell wall of Aram 2 3 bacteria

The bilipid layer is attached to the peptidoglycan byThe bilipid layer is attached to the peptidoglycan bylipoproteinslipoproteins that cross the periplasmic spacethat cross the periplasmic space (@raunGs(@raunGs

lipoproteins: anchors the outer membrane to peptidoglycan + mureinlipoproteins: anchors the outer membrane to peptidoglycan + murein

- sheet ).- sheet ).

The proteins includeThe proteins include porinsporins which form which form transmembranetransmembrane

channelschannels involved in theinvolved in the transport of:transport of: J ions andions and

J

hydrophilic compoundshydrophilic compoundsfrom the e8tracellular compartment to the periplasm.from the e8tracellular compartment to the periplasm.

$orin$orin

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$orin$orin

#unctions of porins#unctions of porins

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#unctions of porins#unctions of porins

/mp C/mp C andand /mp #/mp # porins: proteins that form porins: proteins that form pores or channels through outer membrane for pores or channels through outer membrane for

passage of passage of hydrophilic moleculeshydrophilic molecules

/mp /mp : provides: provides receptor for some virusesreceptor for some viruses andand bacteriocinsbacteriocins (antibiotics produce by some bacteria)(antibiotics produce by some bacteria)$$

stabilies mating cells during conDugation (seestabilies mating cells during conDugation (see

genetic chapter).genetic chapter).

Eram-negative bacteria are surrounded by twoEram-negative bacteria are surrounded by two

bb

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membranes.membranes.

TheThe outer membraneouter membrane functions as an efficientfunctions as an efficient permeability barrier permeability barrier because it contains because it contains

lipopolysaccharideslipopolysaccharides 2"$(32"$(3 and porins.and porins.

;ipoproteins;ipoproteins

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;ipoproteins;ipoproteins

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:01:=:01:=

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:01:=:01:=

*ipopolysaccharide *ipopolysaccharide 2"$(& endoto-in32"$(& endoto-in3

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;,? is composed of a:;,? is composed of a:- lipid portionlipid portion 2lipid 3&2lipid 3&

- aa polysaccharide rich core polysaccharide rich core and a and a

- polysaccharide side chain polysaccharide side chain..

thethe lipid portionlipid portion is heat-stable and responsibleis heat-stable and responsible

for thefor the biologicbiologic effectseffects ofof endoto-inendoto-in$$

thethe polysaccharide rich corepolysaccharide rich core isis antigen R antigen R ofofgram-negative bacteria$gram-negative bacteria$

*ipopolysaccharide *ipopolysaccharide 2"$(& endoto-in32"$(& endoto-in3

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*ipopolysaccharidep p y 2"$(& endoto-in32 & 3

thethe polysaccharide portion of "$(polysaccharide portion of "$( isis antigenicantigenic and is designed as theand is designed as the antigen /antigen /$$

antigen determines electronegativity andantigen determines electronegativity and

hydrophylia of the bacteria thus confershydrophylia of the bacteria thus confers smoothsmoothculture charactersculture characters stabilitystability in suspensions andin suspensions and

antiphagocytic effectsantiphagocytic effects$$

antigen + has group specificityantigen + has group specificity being important being importantfor the identification of bacteriafor the identification of bacteria (using &g-&b(using &g-&b

reaction in the presence of &b that are 4nown)reaction in the presence of &b that are 4nown)..

:1 "$(> 0 'raun lipoproteines> 4 #osfolipide:1 "$(> 0 'raun lipoproteines> 4 #osfolipide

t b $ tid li l o ter membrane> $eptidoglican la er

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outer membrane> $eptidoglican layer outer membrane> $eptidoglican layer

"$("$(

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)he outer membrane

The outer membrane confers several importantThe outer membrane confers several importantpropertiesproperties on Eram-negative bacteria:on Eram-negative bacteria:

- it protects the peptidoglycan from the effects of lysoyme$it protects the peptidoglycan from the effects of lysoyme$- it impedes theit impedes the accesacces of many antibiotics that are thusof many antibiotics that are thus

rendered impotent$rendered impotent$- it alit alllows the access of low molecular weight nutrients$ows the access of low molecular weight nutrients$- components of the ;,? in particular the lipid & formcomponents of the ;,? in particular the lipid & form

endoto)inendoto)in which when released in the blood stream may which when released in the blood stream may

give rise to thegive rise to the endoto-ic shock1endoto-ic shock1


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)he outer membrane

)he periplasmic space)he periplasmic space

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e pe p s c sp cep p p

TheThe periplasmic space periplasmic space is placed between theis placed between theouter membrane and the cytoplasmicouter membrane and the cytoplasmic

membrane.membrane.

t contains thet contains the peptidoglycan& lipoproteinspeptidoglycan& lipoproteinsandand en;ymesen;ymes involved in:involved in:- the e8tracellular digestion of gram-negativethe e8tracellular digestion of gram-negative

bacteria or bacteria orin the inactivation of antibiotics.in the inactivation of antibiotics.


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p p pp p p


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p p pp p p

#unction of peptidoglycan#unction of peptidoglycan

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p p g yp p g y

,eptidoglycan prevents osmotic lysis and,eptidoglycan prevents osmotic lysis andconfers rigidity and shape$confers rigidity and shape$

outer membrane is a permeability barrier$outer membrane is a permeability barrier$

associated ;,? and proteins have variousassociated ;,? and proteins have various

functionsfunctions

#unctions of the cell wall#unctions of the cell wall

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The cell walls of bacteria deserve special attention forThe cell walls of bacteria deserve special attention forseveral reasons:several reasons:1. They are an essential structure for viability as1. They are an essential structure for viability asdescribed above.described above.A. They are composed of uniue componentsA. They are composed of uniue components

(peptidoglycan) found nowhere else in nature.(peptidoglycan) found nowhere else in nature.F. They are one of the most important sites for attac4F. They are one of the most important sites for attac4

by antibiotics by antibiotics (li4e penicillins)(li4e penicillins)..I. They provide ligands for adherence and receptorI. They provide ligands for adherence and receptorsites for drugs or viruses.sites for drugs or viruses.3. They cause symptoms of disease in animals.3. They cause symptoms of disease in animals.2. They provide for immunological distinction and2. They provide for immunological distinction andimmunological variation among strains of bacteria.immunological variation among strains of bacteria.

cid 7 fast bacillicid 7 fast bacilli

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'cidfast bacilli 'cidfast bacilli (mycobacteria but also other(mycobacteria but also otherfilamentous bacteria such asfilamentous bacteria such as ocardia ocardia) resist) resist

destaining withdestaining with acid7alcoholacid7alcohol after stainingafter staining

with carbol-fuchsin in Kiehl-*eelsen stainingwith carbol-fuchsin in Kiehl-*eelsen stainingso they stainso they stain red.red.

cid 7 fast bacilli 2cid 7 fast bacilli 2redred33

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22 33

cid 7 fast bacillicid 7 fast bacilli

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The basis for the staining is the presence of uniue fattyThe basis for the staining is the presence of uniue fatty

acids (e.g.acids (e.g. mycolic acidsmycolic acids) in the cell wall.) in the cell wall.

&rabinogalactan and mycolic acids: dictate the resistance&rabinogalactan and mycolic acids: dictate the resistancein decoloriation and resistance to environment factors.in decoloriation and resistance to environment factors.

?urface lipids (including corde factor): change M in giant?urface lipids (including corde factor): change M in giantcells and granuloma as main lesion.cells and granuloma as main lesion.

Mycoide: e8ternal barrier that allow survival inMycoide: e8ternal barrier that allow survival ininflammatory celsinflammatory cels

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The high content ofThe high content of wa-wa- andand lipidslipids of the cellof the cellwall confers thewall confers the acid7fast bacilli resistanceacid7fast bacilli resistance totoantimicrobial agents, heat, dryness, chemicalantimicrobial agents, heat, dryness, chemical

agentsagents..

They areThey are facultatie intracellularfacultatie intracellular organismsorganismsand they survive in macrophage cells.and they survive in macrophage cells.

&cid - fast bacilli (mycolic acids arabinogalactan)&cid - fast bacilli (mycolic acids arabinogalactan)

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>ell 9all-less =orms>ell 9all-less =orms

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& few bacteria are able to live or e8ist without a cell wall.& few bacteria are able to live or e8ist without a cell wall.

There are two groups of bacteria that lac4 the protectiveThere are two groups of bacteria that lac4 the protective

cell wall peptidoglycan structure thecell wall peptidoglycan structure the

Mycoplasma Mycoplasma species one of which causes atypicalspecies one of which causes atypical pneumonia ( pneumonia ( M. pneumoniae M. pneumoniae and some genitourinary tractand some genitourinary tract

infectionsinfections (M. hominis(M. hominis and theand the

"7forms&"7forms& which originate from Eram-positive or Eram-which originate from Eram-positive or Eram-

negative bacteria and are so designated because of theirnegative bacteria and are so designated because of their

discovery and description at the ;ister nstitute ;ondon.discovery and description at the ;ister nstitute ;ondon.


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TheThe mycoplasmas and "7forms are all Aram7negatiemycoplasmas and "7forms are all Aram7negatieand insensitive to penicillin and are bounded by a surfaceand insensitive to penicillin and are bounded by a surfacemembrane structure.membrane structure.

;-forms arising LspontaneouslyL in cultures or isolated;-forms arising LspontaneouslyL in cultures or isolatedfrom infections are structurally related to protoplasts andfrom infections are structurally related to protoplasts and

spheroplasts$spheroplasts$ (pheroplasts(pheroplasts (that lost their cell wall from Eram(that lost their cell wall from Eram

negativenegative bacteria) bacteria)&& andand "7forms reert infreuently and"7forms reert infreuently andonly under special conditionsonly under special conditions..

9hen protoplast become “nude” (with no cell wall9hen protoplast become “nude” (with no cell wallcompletely)completely) protoplastsprotoplasts (that lost their cell wall of Eram(that lost their cell wall of Eram positive positive bacteria) bacteria) can not reert to the main bacteria1can not reert to the main bacteria1


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The mycoplasmas are a group of bacteria thatThe mycoplasmas are a group of bacteria thatlac4 a cell wall.lac4 a cell wall.

Mycoplasmas have sterol-li4e moleculesMycoplasmas have sterol-li4e molecules

incorporated into their membranes and theyincorporated into their membranes and theyare usually inhabitants of osmotically-are usually inhabitants of osmotically- protected environments. protected environments.

Mycoplasma pneumoniae Mycoplasma pneumoniae is the cause ofis the cause of

primary atypical bacterial pneumonia 4nown primary atypical bacterial pneumonia 4nownas Lwal4ing pneumoniaL.as Lwal4ing pneumoniaL.


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=or obvious reasons penicillin is ineffective in=or obvious reasons penicillin is ineffective intreatment of this type of pneumonia.treatment of this type of pneumonia.

?ometimes under the pressure of antibiotic therapy?ometimes under the pressure of antibiotic therapy pathogenic streptococci can revert to cell wall-less pathogenic streptococci can revert to cell wall-less

forms (call protoplasts) and persist or survive informs (call protoplasts) and persist or survive in

osmotically-protected tissues.osmotically-protected tissues.

,'T,;&?T?,'T,;&?T?

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Complete remoalComplete remoal of theof the bacterial cell wallbacterial cell wall of aof aAram7positieAram7positie bacterium results in the formation of bacterium results in the formation of

protoplasts protoplasts which are constituted by the cytoplasmic which are constituted by the cytoplasmicmembrane and the bacterial contents.membrane and the bacterial contents.

,rotoplasts reuire an isotonic medium in order to,rotoplasts reuire an isotonic medium in order toassume a spherical configuration$assume a spherical configuration$

they cannot maintain integrity when placed in a hypo-they cannot maintain integrity when placed in a hypo-or hypertonic medium.or hypertonic medium.

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;-='M?;-='M?

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*forms *forms (wall-less organisms) may emerge during(wall-less organisms) may emerge duringantibiotic therapy. These aberrant organisms canantibiotic therapy. These aberrant organisms can

cause persistentcause persistent infection resisting the effects ofinfection resisting the effects of

antibiotics whose mechanism of action involvesantibiotics whose mechanism of action involves

interference with cell wall formation.interference with cell wall formation. They differ from the parent bacteria inThey differ from the parent bacteria in lacking alacking a

rigid cell wallrigid cell wall and in conseuence regular sie andand in conseuence regular sie and

shape but they are nevertheless viable and capable ofshape but they are nevertheless viable and capable ofgrowing and multiplying on a suitable nutrientgrowing and multiplying on a suitable nutrient

medium.medium.

41 (tructures present in some strains of41 (tructures present in some strains ofsome species*some species* are not useful forare not useful for

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ta-onomyta-onomy

fimbriae (common pili)fimbriae (common pili)

se8 pili$se8 pili$

glicocali-glicocali- (capsule microcapsule loose(capsule microcapsule loose

slime).slime).

>&,?";!? M>'>&,?";!? &*7>&,?";!? M>'>&,?";!? &*7

;?! ?;M!;?! ?;M!

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;?! ?;M!;?! ?;M!

Many bacteria including several pathogenicMany bacteria including several pathogenicspecies are surrounded by a discrete coveringspecies are surrounded by a discrete covering

layer of a relatively firm gelatinous materiallayer of a relatively firm gelatinous material

that lies outside and immediately in contactthat lies outside and immediately in contactwith the cell wallwith the cell wall 22 glicocali) glicocali) 3131

MicrocapsuleMicrocapsule

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9hen this layer in the wet state is wide9hen this layer in the wet state is wideenough (C.Aenough (C.A µµm or more) to be resolved withm or more) to be resolved with

the light microscope it is called athe light microscope it is called a capsulecapsule11

9hen it is narrower and detectable only by9hen it is narrower and detectable only byindirect serological means or by electronindirect serological means or by electron

microscopy it may be termed amicroscopy it may be termed a microcapsulemicrocapsule11

MicrocapsuleMicrocapsule

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The capsular gel consists largely of water andThe capsular gel consists largely of water andit has only a small content of solids (e.g. A).it has only a small content of solids (e.g. A).

n most species the solid material is a comple8n most species the solid material is a comple8

polysaccharidepolysaccharide though in some species its though in some species itsmain constituent ismain constituent is polypeptidepolypeptide or or proteinprotein..

!8tracellular polymer is synthesied by!8tracellular polymer is synthesied by

enymes located at the surface of the bacterialenymes located at the surface of the bacterialcell.cell.

"oose slime"oose slime

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*oose slime *oose slime or or free slime free slime is an amorphous is an amorphousviscid colloidal material that is secretedviscid colloidal material that is secreted

e8tracellularly by some non-capsulate bacteriae8tracellularly by some non-capsulate bacteria

and also outside their capsules by manyand also outside their capsules by manycapsulate bacteria.capsulate bacteria.

n capsulate bacteria the slime is generallyn capsulate bacteria the slime is generally

similar in chemical composition and antigenicsimilar in chemical composition and antigeniccharacter to the capsular substance.character to the capsular substance.

?lime forming bacteria. >apsular slime?lime forming bacteria. >apsular slime

surrounding bacterial cell is clearly visiblesurrounding bacterial cell is clearly visible

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Capsule,s functionsCapsule,s functions

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t is probable that the principal action oft is probable that the principal action ofcapsules and microcapsules is tocapsules and microcapsules is to protectprotect thethe

cell wall against attac4 by various 4inds ofcell wall against attac4 by various 4inds of

antibacterial agents e.g. bacteriophagesantibacterial agents e.g. bacteriophagescolicines complement lysoyme and othercolicines complement lysoyme and other

lytic enymes that otherwise would morelytic enymes that otherwise would more

readily damage and destroy it.readily damage and destroy it.


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n the case of certain capsulaten the case of certain capsulate pathogenicpathogenic organismsorganisms(e.g. pneumococcus pyogenic streptococci anthra8(e.g. pneumococcus pyogenic streptococci anthra8

bacillus) good evidence has been obtained to show bacillus) good evidence has been obtained to showthat thethat the capsule protects the bacteria againstcapsule protects the bacteria against

ingestion by the phagocytes of the hostingestion by the phagocytes of the host .. The capsule is thus an important agent determiningThe capsule is thus an important agent determining

irulenceirulence and non-capsulate mutants of theseand non-capsulate mutants of these bacteria are found to be non-virulent. bacteria are found to be non-virulent.

The capsule is also involved in theThe capsule is also involved in the adherenceadherence ofof bacteria to different surfaces including hostGs cells. bacteria to different surfaces including hostGs cells.


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The capsular substance is usuallyThe capsular substance is usually antigenicantigenic and the capsular antigens play a veryand the capsular antigens play a veryimportant part in determining the antigenicimportant part in determining the antigenicspecificity of bacteria.specificity of bacteria.

9hen capsulate pneumococci are treated with9hen capsulate pneumococci are treated withtype-specific antiserum the sharpness oftype-specific antiserum the sharpness ofoutline of the capsule is greatly enhanced. Thisoutline of the capsule is greatly enhanced. This

is referred to as the Lis referred to as the L capsule#s$ellingcapsule#s$ellingreactionreaction L.L.

TheThe capsule is colorless in usual stainingscapsule is colorless in usual stainings..

EECapsuleswelling reactionCapsuleswelling reactionEE

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flagella>flagella>

spores$spores$

inclusion granules.inclusion granules.

=;&E!;;&=;&E!;;&

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@acteria may have the following appendages:

flagella and pilliflagella and pilli Motile bacteria possess filamentous appendages 4nown asMotile bacteria possess filamentous appendages 4nown as

flagella which act as organs of lflagella which act as organs of locomotionocomotion.. The flagellum is a long thin filament twisted spirally in aThe flagellum is a long thin filament twisted spirally in a

wave form.wave form. t is about C.CAt is about C.CA µµm thic4 and is usual several times them thic4 and is usual several times the

length of the bacterial cell.length of the bacterial cell. tt originates in the bacterial protoplasmoriginates in the bacterial protoplasm and is e8trudedand is e8truded

through the cell wall.through the cell wall. &ccording to the species there may be one to several (e.g.&ccording to the species there may be one to several (e.g.

1-AC) flagella per cell.1-AC) flagella per cell.

=;&E!;;&=;&E!;;&

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)he arrangement of flagella)he arrangement of flagella

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The arrangement of flagella may beThe arrangement of flagella may bemonotrichusmonotrichus + a single flagellum at one end of + a single flagellum at one end ofthe bacteriumthe bacterium amphitrichousamphitrichous + two flagella + two flagellaeach at one end of the bacteriumeach at one end of the bacterium lofotrichouslofotrichous

+ a group of flagella at one end of the + a group of flagella at one end of the bacterium or bacterium or peritrichous peritrichous when they when theyoriginate over the surface of the cell.originate over the surface of the cell.

The presence number and position of theThe presence number and position of theflagella areflagella are primary ta-onomicprimary ta-onomic criteriacriteria

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=lagella=lagella

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=lagella consist largely or entirely of a=lagella consist largely or entirely of aproteinprotein flagellin flagellin belonging to the same belonging to the samechemical group as myosin the contractilechemical group as myosin the contractile protein of muscle and are driven by the rotary protein of muscle and are driven by the rotaryaction of a swivel-li4e basal hoo4.action of a swivel-li4e basal hoo4.

They can be demonstrated easily and clearlyThey can be demonstrated easily and clearlywith thewith the electron microscopeelectron microscope ussually ussually

appearing as simple fibrils without internalappearing as simple fibrils without internaldifferentiation.differentiation.

=lagella=lagella

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They are invisible by the light microscope butThey are invisible by the light microscope butmay be shown by the use ofmay be shown by the use of special stainingspecial staining

methodsmethods (e.g. silver staining) and in special(e.g. silver staining) and in special

circumstances by dar4-ground illumination.circumstances by dar4-ground illumination. @ecause of the difficulties of these methods@ecause of the difficulties of these methods

the presence of flagella is commonly inferredthe presence of flagella is commonly inferred

from the observation of motility.from the observation of motility.

%ofotrichous %ofotrichous flagellaflagella

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'acterial #lagellum (tructure'acterial #lagellum (tructure

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MotilityMotility

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Motility may be observed eitherMotility may be observed either microscopicallymicroscopically oror by noting the by noting the occurence of spreading growth in semi-occurence of spreading growth in semi-solid agar mediumsolid agar medium..

nn microscopicalmicroscopical observation ofobservation of wet filmswet films motilemotile

bacteria are seen swimming in different directions bacteria are seen swimming in different directionsacross the field with a darting wriggling or tumblingacross the field with a darting wriggling or tumblingmovement.movement.

True motility must be distinguished from a drifting ofTrue motility must be distinguished from a drifting ofthe bacteria in a single direction due to a curent in thethe bacteria in a single direction due to a curent in the

liuid and also from the @rownian movement whichliuid and also from the @rownian movement whichis a rapid oscillation of each bacterium within a veryis a rapid oscillation of each bacterium within a verylimited area due to bombardment by water molecules.limited area due to bombardment by water molecules.

(emisolid agar(emisolid agar

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MotilityMotility

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&mong the&mong the spirochetespirochete motility appears to be a motility appears to be afunction of the cell body since flagella do not occur.function of the cell body since flagella do not occur.

The most characteristic movement is a fast spiralThe most characteristic movement is a fast spiral

rotation on the long a8is with slow progression in therotation on the long a8is with slow progression in the

a8ial line$ movements of fle8ion and lashinga8ial line$ movements of fle8ion and lashing

movements may be observed.movements may be observed.

?ome spirochetes possess an?ome spirochetes possess an a-ial filamenta-ial filament andand

others aothers a band of fibrilsband of fibrils wound around their surfacewound around their surfacefrom pole to pole.from pole to pole.

(pirochete,s flagella(pirochete,s flagella

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(pirochete,s flagella(pirochete,s flagella

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-reponema-reponema andand orrelia orrelia have numerous thinhave numerous thin a-iala-ialfilamentsfilaments disposed around the protoplast disposed around the protoplast

whilewhile *eptospira *eptospira has only two thic4er filamentshas only two thic4er filaments

forming anforming an a-istila-istil surrounded by the protoplast. surrounded by the protoplast.

t has been suggested that these structures mayt has been suggested that these structures may

contribute to motility either through beingcontribute to motility either through being

themselves contractile or by acting as stiffeners forthemselves contractile or by acting as stiffeners for

recoil against the contractile protoplast.recoil against the contractile protoplast.

MotilityMotility

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Motility may be beneficial in increasing theMotility may be beneficial in increasing therate of upta4e of nutrient solutes byrate of upta4e of nutrient solutes by

continuously changing the environmental fluidcontinuously changing the environmental fluid

in contact with the bacterial cell surface.in contact with the bacterial cell surface. 'andom movement and dispersion through the'andom movement and dispersion through the

environment may be beneficial ensuring that atenvironment may be beneficial ensuring that at

least some cells of the strain reach everyleast some cells of the strain reach everylocality suitable for coloniation.locality suitable for coloniation.

MotilityMotility

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@acteria tend to migrate towards regions@acteria tend to migrate towards regionswhere there is a higher concentration ofwhere there is a higher concentration of

nutrient solutes (a process 4nown asnutrient solutes (a process 4nown as

chemota&ischemota&is) and away from regions containing) and away from regions containinghigher concentrations of disinfectanthigher concentrations of disinfectant

substances (substances (negative chemota&isnegative chemota&is).).

MotilityMotility

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t might be supposed that the power of activet might be supposed that the power of activelocomotion would assist pathogenic bacteria inlocomotion would assist pathogenic bacteria in

penetrating through viscid mucous secretions penetrating through viscid mucous secretions

and epithelial barriers and in spreadingand epithelial barriers and in spreadingthroughout the body fluids and tissue but itthroughout the body fluids and tissue but it

must be noted that many non-motile pathogensmust be noted that many non-motile pathogens

(e.g. brucellae and streptococci) are no less(e.g. brucellae and streptococci) are no less

invasive than motile ones.invasive than motile ones.

41 (tructures present in some strains of41 (tructures present in some strains ofsome species*some species* are not useful forare not useful for

ta-onomyta-onomy

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ta-onomyta-onomy

fimbriae 2common pili3fimbriae 2common pili3

se8 pili$se8 pili$

glicocali-glicocali- (capsule microcapsule loose(capsule microcapsule loose

slime).slime).

$illi$illi Common pilliCommon pilli:: arround the surface of Eram negative bacteria.arround the surface of Eram negative bacteria.

?tructure: pillin (is a protein)?tructure: pillin (is a protein)

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?tructure: pillin (is a protein)?t uctu e: p ( s a p ote )

=unction:=unction: attachmentattachment essential in coloniation essential in coloniation =imbriae are also=imbriae are also antigenic and secretory antibodiesantigenic and secretory antibodies (g&) will often(g&) will often

bloc4 bacterial coloniation while circulating antibodies (gE or gM) bloc4 bacterial coloniation while circulating antibodies (gE or gM)

will opsonie bacterial cells for phagocytosiswill opsonie bacterial cells for phagocytosis ((specific antibodies arespecific antibodies are

useful for host defence and for diagnosis).useful for host defence and for diagnosis).

(e- pilli(e- pilli:: mediates the transfer of 7*& between mating bacteria but themediates the transfer of 7*& between mating bacteria but thefunction of the smaller more numerous common pili is uite different.function of the smaller more numerous common pili is uite different.

Many bacteria are able to e8change genes for virulence by means ofMany bacteria are able to e8change genes for virulence by means of

conDugation the se8 pilus which confers the ability to conDugate mayconDugation the se8 pilus which confers the ability to conDugate may

well play a role in the their assembly of virulence determinants.well play a role in the their assembly of virulence determinants.

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flagella>flagella>

spores>spores>

inclusion granules.inclusion granules.

(pore(pore

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?ome species notably those of the genera?ome species notably those of the genera Bacillus Bacillus andand ClostridiumClostridium develop a develop a highlyhighly

resistantresistant structure orstructure or endosporeendospore whereby the whereby the

organism can survive in a dormant stateorganism can survive in a dormant statethrough a long period of starvation or otherthrough a long period of starvation or other

adverse environmental condition.adverse environmental condition.

(porulation(porulation versusversus germinationgermination

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The process does not involve multiplication:The process does not involve multiplication: inin sporulation sporulation each vegetative cell forms only each vegetative cell forms only

one spore and in subseuentone spore and in subseuent

germination germination each spore gives rise to a singleeach spore gives rise to a singlevegetative cell.vegetative cell. >ertain specific antigens develop in the spore>ertain specific antigens develop in the spore

that are not found in the vegetative cells.that are not found in the vegetative cells. ?pores are involved in the?pores are involved in the transmissiontransmission ofof

certain diseases.certain diseases.

$porulation $porulation

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$porulation $porulation occurs as a response to starvation or atoccurs as a response to starvation or atleast the e8haustion of a limiting substance.least the e8haustion of a limiting substance.

n certain species sporulation may be induced byn certain species sporulation may be induced bydepletion of nutrients necessary for vegetativedepletion of nutrients necessary for vegetative

growth$growth$ at the same time the process reuires a continuedat the same time the process reuires a continued

supply of other minerals (potassium magnesiumsupply of other minerals (potassium magnesiummanganese and calcium salts) and favorablemanganese and calcium salts) and favorable

conditions of moisture temperature p5 o8ygenconditions of moisture temperature p5 o8ygentension etc.tension etc.

(porulation(porulation

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The spore is formed inside the parent vegetative cellThe spore is formed inside the parent vegetative cell(hence the name “endospore”).(hence the name “endospore”).

t develops from a portion of the protoplasm near onet develops from a portion of the protoplasm near oneend of the cell (“the forespore”) incorporates part of theend of the cell (“the forespore”) incorporates part of the

nuclear material (euivalent to one genome) of the cellnuclear material (euivalent to one genome) of the celland auires a thic4 covering layerand auires a thic4 covering layer the “the “corte-corte-” and” and a thin but tough outer “a thin but tough outer “spore coatspore coat” consisting of” consisting of

several layers.several layers. ?pores of some species have an additional apparently?pores of some species have an additional apparently

rather loose covering 4nown as the “rather loose covering 4nown as the “e-osporiume-osporium”.”.

(pore(pore,,s structures structure

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(hape& dispo;ition(hape& dispo;ition

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TheThe appearance of the mature sporeappearance of the mature spore variesvariesaccording to the speciesaccording to the species being spherical&being spherical&

ooidooid or or elongated& occupying a terminal&elongated& occupying a terminal&

subterminalsubterminal or or central position&central position& and beingand beingnarrower than the cell or broader and bulgingnarrower than the cell or broader and bulging

it.it.

=inally the remainder of the parent cell=inally the remainder of the parent cell

disintegrates and the spore is freed.disintegrates and the spore is freed.

C C lostridiumlostridium

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C.C. t t etani etani 2culture smear32culture smear3

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acillus acillus 2culture smear32culture smear3

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acillus anthracis acillus anthracis 2the lack of spore2the lack of spore

in vivoin vivo . capsule3 . capsule3

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acillus cereus acillus cereus 2culture smear32culture smear3

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(pore,s dispo;ition(pore,s dispo;ition

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pplicationpplication

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?pores are much more resistant than the?pores are much more resistant than thevegetative forms to inDurious chemical andvegetative forms to inDurious chemical and physical influences including e8posure to physical influences including e8posure todisinfectants drying and heating.disinfectants drying and heating.

Thus application of moist heat at 1CC-1ACThus application of moist heat at 1CC-1AC°°>>for a period of 1C-AC minutes may be neededfor a period of 1C-AC minutes may be neededto 4ill spores whereas heating at 2Cto 4ill spores whereas heating at 2C°°> suffices> suffices

to 4ill vegetative cells$ spores can be used into 4ill vegetative cells$ spores can be used inthethe control of sterili;ationcontrol of sterili;ation..

(pore F resistance(pore F resistance

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?pores may remain viable for many years either in?pores may remain viable for many years either inthe dry state or in moist conditions unfavorable tothe dry state or in moist conditions unfavorable togrowth.growth.

The mar4ed resistance of spores has been attributedThe mar4ed resistance of spores has been attributed

to several factors in which they differ from vegetativeto several factors in which they differ from vegetativeforms:forms:

- the impermeability of their corte8 and outer coatthe impermeability of their corte8 and outer coat- their high content of calcium and dipicolinic acidtheir high content of calcium and dipicolinic acid

- their low content of water and theirtheir low content of water and their- very low metabolic and enymatic-activity.very low metabolic and enymatic-activity.

GerminationGermination

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'ermination'ermination of the spore occurs when theof the spore occurs when thee8ternal conditions become favorable toe8ternal conditions become favorable to

growth by access to moisture and nutrients.growth by access to moisture and nutrients.

t is irreversible and involves rapid degradativet is irreversible and involves rapid degradativechanges.changes.


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The spore successively loses its heat resistanceThe spore successively loses its heat resistanceand its dipicolinic acid$ it loses calcium itand its dipicolinic acid$ it loses calcium it

becomes permeable to dyes and its refractility becomes permeable to dyes and its refractility

changes.changes. n the process of germination the spore swellsn the process of germination the spore swells

its corte8 disintegrates its coat is bro4en and aits corte8 disintegrates its coat is bro4en and a

single vegetative cell emerges.single vegetative cell emerges.


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9hen mature the spore resists coloration by9hen mature the spore resists coloration bysimple stains appearing as asimple stains appearing as a clear spaceclear space

within the stained cell protoplasm.within the stained cell protoplasm.

?pores are slightly acid-fast and may be?pores are slightly acid-fast and may bestained differentially by a modification of thestained differentially by a modification of the

Kiehl-*eelsen method.Kiehl-*eelsen method.

acillus acillus 2culture smear32culture smear3

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(pore(pore

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TheThe presence& shape and positionpresence& shape and position of theof thespores arespores are primary ta-onomic charactersprimary ta-onomic characters ofof

bacteria. bacteria.

(pore,s dispo;ition(pore,s dispo;ition

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'acterial reproduction'acterial reproduction

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&mong bacteria multiplication ta4es place by&mong bacteria multiplication ta4es place by simplesimplebinary fissionbinary fission11

The cell grows in sie usually elongating to twice itsThe cell grows in sie usually elongating to twice its

original length and the protoplasm becomes dividedoriginal length and the protoplasm becomes dividedinto two appro8imately eual parts by the ingrowth ofinto two appro8imately eual parts by the ingrowth ofa transverse septum from the plasma membrane anda transverse septum from the plasma membrane andcell wall.cell wall.

n some species the cell wall septum or cross-walln some species the cell wall septum or cross-wall

splits in two and the daughter cells separate almostsplits in two and the daughter cells separate almostimmediately.immediately.

'acterial reproduction'acterial reproduction

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n others the cell wall of the daughter cells remainn others the cell wall of the daughter cells remaincontinuous for some time after cell division and thecontinuous for some time after cell division and theorganisms grow adhering in pairs clusters chains ororganisms grow adhering in pairs clusters chains orfilaments.filaments.

f cross-wall splitting is thus delayed in an organismf cross-wall splitting is thus delayed in an organism

in which the cross-walls of successive cell divisionsin which the cross-walls of successive cell divisionsare all formed in parallel planes the cells will beare all formed in parallel planes the cells will begrouped in chains.grouped in chains.

f it is delayed in an organism that forms successivef it is delayed in an organism that forms successive

cross-walls in different planes e.g. ones at rightcross-walls in different planes e.g. ones at rightangles to each other the cells will be grouped inangles to each other the cells will be grouped in pairs forming either cubic or irregular clusters. pairs forming either cubic or irregular clusters.

Cells, diisionCells, diision

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5nternal (tructure: @acteria have a very simpleinternal structure and no membrane-bound organelles.

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nucleoid

7*& in the bacterial cell is generallyconfined to this central region. Thoughit isn0t bounded by a membrane it isvisibly distinct (by transmissionmicroscopy) from the rest of the cellinterior.

ribosomes

'ibosomes give the cytoplasm of bacteria a granular appearance inelectron micrographs. Though smaller

than the ribosomes in eu4aryotic cellsthese inclusions have a similar functionin translating the genetic message inmessenger '*& into the production of

peptide seuences (proteins).

5nternal (tructure: @acteria have a very simpleinternal structure and no membrane-bound organelles.

*utrients and reserves may be stored in

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storagegranules

*utrients and reserves may be stored in

the cytoplasm in the form of glycogenlipids polyphosphate or in some casessulfur or nitrogen.

endospore

?ome bacteria li4e Clostridiumbotulinum form spores that are highlyresistant to drought high temperatureand other environmental haards. ncethe haard is removed the sporegerminates to create a new population.

(urface (tructure: @eginning from theoutermost structure and moving inward bacteria

have some or all of the following structures

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capsule

This layer of polysaccharide (sometimes proteins) protects the bacterial cell and isoften associated with pathogenic bacteria because it serves as a barrier against phagocytosis by white blood cells.

outer membrane

This lipid bilayer is found in Eram

negative bacteria and is the source oflipopolysaccharide (;,?) in these bacteria.;,? is to8ic and turns on the immunesystem of but not in Eram positive bacteria.

cell wall

>omposed of peptidoglycan(polysaccharides N protein) the cell wallmaintains the overall shape of a bacterialcell. The three primary shapes in bacteriaare coccus (spherical) bacillus (rod-shaped) and spirillum (spiral).Mycoplasma are bacteria that have no cell

ll d th f h d fi it h

:

(urface (tructure periplasmic space

This cellular compartment is found only in those bacteria that

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have both an outer membrane and plasma membrane (e.g.Eram negative bacteria). n the space are enymes and other

proteins that help digest and move nutrients into the cell.

plasma membrane

This is a lipid bilayer much li4e the cytoplasmic (plasma)membrane of other cells. There are numerous proteins moving

within or upon this layer that are primarily responsible for

transport of ions nutrients and waste across the membrane.

ppendages: @acteria may have the following

appendages:

These hollow hairli4e structures made of

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pili

These hollow hairli4e structures made of protein allow bacteria to attach to othercells. & specialied pilus the se8 pilusallows the transfer of plasmid 7*& fromone bacterial cell to another. ,ili (sing.

pilus) are also called fimbriae (sing.

fimbria).

flagella

The purpose of flagella (sing. flagellum)is motility. =lagella are long appendageswhich rotate by means of a LmotorLlocated Dust under the cytoplasmic

membrane. @acteria may have one afew or many flagella in different

positions on the cell.

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*ote: all photos from this presentation can not *ote: all photos from this presentation can not be citated without permission of their authors be citated without permission of their authors

(that can be found on the internet)(that can be found on the internet)

These photos are not the properties of authorGsThese photos are not the properties of authorGslecture or of "niversity and you can notlecture or of "niversity and you can not

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