Download - Morphology and structure of bacteria Oral Microbiology for dentistry MUDr. Lenka Černohorská, Ph.D
Morphology and structure of Morphology and structure of bacteriabacteria
Oral Microbiology for dentistry
MUDr. Lenka MUDr. Lenka ČČernohorskernohorská, Ph.D.á, Ph.D.
Size of bacteriaSize of bacteria
Pathogenic bacteria: mainly around Pathogenic bacteria: mainly around 1 – 5 1 – 5 μmμm (1 μm = 10 (1 μm = 10-3-3 mm) mm)
Staphylococcus: the diameter circa Staphylococcus: the diameter circa 1 μm1 μm Even Even smallersmaller: :
rickettsiae (circa 0.5 μm) rickettsiae (circa 0.5 μm) chlamydiae (elementary bodies circa 0.3 μm) chlamydiae (elementary bodies circa 0.3 μm) mycoplasmas (circa 0.2 – 0.25 μm ) mycoplasmas (circa 0.2 – 0.25 μm )
Various shapes of bacteriaVarious shapes of bacteria
• Cocci (spherical)Cocci (spherical)• Rods /bacilli:Rods /bacilli:
can be shortcan be short
longlong
robust, thinrobust, thin
• Spirochaete (helical)Spirochaete (helical)
Common bacterial formsCommon bacterial forms
• Cocci in chains – streptococci
• Cocci in clusters – staphylococci
• Cocci in pairs – diplococci (neisseria)
• Bacilli in chains
• Curved bacilli
• Spore-bearing bacilli
Structures II.Structures II.
CytoplasmCytoplasm - is enclosed within the cell membrane, contains organelles. Here occur most cellular activities and metabolic pathways. The part of the cytoplasm that is not held within organelles is called the cytosol (a gel, with a network of fibers dispersed through water)
CapsuleCapsule – gelatinous layer around the bacterium is composed of polysaccharides, proteins – inhibits phagocytosis, helps the adhesion, is used in preparation of vaccines
FimbriaeFimbriae – hair-like filaments, mediate adhesion to receptors
InclusionsInclusions – serve as sources of stored energy (polysaccharides)
Gram-staining Gram-staining (more in practical lessons)(more in practical lessons)
• Crystal violetCrystal violet – 30 s
• Iodine solutionIodine solution – 30 s
• AlcoholAlcohol – decolorize until violet is removed
• SafraninSafranin – 60 s
G+ purple groupsG- pink groups
Cell wallCell wallResults:• different in G- and G+ bacteria• principle of Gram staining is still unknown, but
it is used for hundred years • G+: Crystal violet attaches to peptidoglycan
(PG) than arise complex with IodineIodine, complex is not washed by alcohol, that is why the final result is purplepurple.
• G-: Little amount of PG inside a cell wall, a little complex/no complex? is washed by alcohol, Safranin is needed for visualisation.
Examples ofExamples of G+G+ andand G–G– microbesmicrobes
Gram-positives Gram-positives
StaStaphylococcusphylococcus
StreptococcusStreptococcus
BacillusBacillus
ClostridiumClostridium
ListeriaListeria
CorynebacteriumCorynebacterium
Yeasts Yeasts
Gram-negativesGram-negatives
EscherichiaEscherichia
SalmonellaSalmonella
Haemophilus Haemophilus
PseudomonasPseudomonas
MycoplasmaMycoplasma
FlagellaFlagella • filaments composed of flagellin flagellin
• responsible for movement movement of bacteria
May be located: (cocci and bacilli)
• at one end:monotrichous, a single flagellum
lophotrichous – many flagella
• all over the outer surface – peritrichous
• Spirochaets move by using the axial filamentaxial filament – produce undulation motion
Sporulation (bacterial winter sleep)Sporulation (bacterial winter sleep)
• In bad conditions some kind of bacteria sporulate
• Spora contains a high concentration of calcium dipicolinate, is resistant to heat, radiation, chemicals, dehydratation, it can remain for many years
• Better conditions- spore transform itself into reproducing bacterial cell again.
Spores - factsSpores - facts
• Spore contains: DNA, small amount of cytoplasm, cell membrane, peptidoglykan, very little water, thick keratin-like coat (with calcium dipicolinate)
Relevance of bacterial sporesRelevance of bacterial spores
• Resistance to heat and chemicals!
• They cannot be easily achieved by boiling
• Other methods of sterilisation like autoclaving should be used
• So for ex. Bacillus stearothermophilusBacillus stearothermophilus is used for evaluation of the sterilisation efficacy of autoclaves!
Types of sporesTypes of spores
1, 4 – central
2, 3, 5 – terminal
6 - lateral
2 – with inclusions
3, 4, 5, 6 – spores deforming a bacterial cell
1, 2 – spores not deforming