“Discuss with examples how the trophic diversity of bacteria can help solve some environmental problems”

Heterotrophics Bacteria Optimizing Carbon-Nitrogen (CN) Ratios for a Healthy Aquaculture Environment

Heterotrophic is the term given to describe bacteria that derive nutrition from

sources that are primarily organic. Heterotrophic bacteria include both probiotic and

pathogenic bacteria types. Probiotic and pathogenic bacteria both naturally occur in

agriculture environments. As their primary source of nutrition is organic compounds,

heterotrophic bacteria are exceptionally useful in breaking down organic wastes

produced by fish. Heterotrophic bacteria rely on two nutrients to thrive, nitrogen and

carbon. As anyone in the aquaculture industry knows, nitrogen is in abundance in a

pond environment. Fish wastes are extremely rich in nitrogen, which, when in excess

can lead to dangerous water chemistry problems. With Nitrogen in

abundance, growth of heterotrophic bacteria is limited by the amount of carbon that

is available to consume. The goal of optimizing carbon: Nitrogen ratios (CN Ratio) is

to increase the level of carbon to an appropriate ratio to allow heterotrophic bacteria

to thrive. If this is achieved then the bacteria will be able to break down the Nitrogen-

rich fish wastes and reduce the ammonia content in the water.

Ammonia released directly by the fish by diffusion from the blood across the

gill membranes. Excreted urea or uric acid is also converted to ammonia through a

process called mineralization. Solid organic, nitrogenous, waste material is also

converted to ammonia through mineralization. Sources of this waste material are

from fecal material, the decay of plant and animal tissues, and from the decay of

excess food. Mineralization is accomplished by any of a number of species of

heterotrophic bacteria. Species from the genus Bacillus are the most common.

Ammonia is the primary compound produced by this process. Some species

of heterotrophic bacteria can oxidize or reduce nitrogenous compounds directly to

nitrites (NO2), nitrate (NO3), or other forms of nitrogen (as NO or N2). In the

absence of an organic nitrogen source, many heterotrophy can utilize ammonia

instead. This is much more likely to happen in the laboratory under ideal conditions

than in actual practice. In the aquarium, as in nature, an organic, nitrogen rich, food

source is constantly being produced and is readily available for these bacteria to

utilize. Heterotrophic bacteria have little or no need to resort to utilizing ammonia as

their source of nitrogen.

This ability of heterotrophic bacteria to utilize ammonia has led to the

erroneous belief that they are as effective as true nitrifying bacteria in establishing

the nitrogen cycle. These bacteria, however, generally cannot utilize nitrites.

Experimental data has shown that up to one million times more of these

heterotrophic ‘nitrifers’ are required to perform a comparable level of ammonia

conversion that is attained by true autotrophic nitrifies. When using heterotrophic

‘nitrifiers’, the nitrogen cycle in the aquarium basically follows the same course as

when no bacteria are added and the system cycles naturally.

Autotrophics Bacteria

- Help Forests Grow

 Bacteria living in mosses on tree branches twice as effective at 'fixing' nitrogen

as those on the ground. The cyanobacteria take nitrogen from the atmosphere and

make it available to plants-a process called "nitrogen fixation" that very few

organisms can do. The growth and development of many forests is thought to be

limited by the availability of nitrogen. Cyanobacteria in mosses on the ground were

recently shown to supply nitrogen to the Boreal forest, but until now cyanobacteria

have not been studied in coastal forests or in canopies (tree-tops). By collecting

mosses on the forest floor and then at 15 and 30 metres up into the forest canopy,

the cyanobacteria are more abundant in mosses high above the ground, and that

they "fix" twice as much nitrogen as those associated with mosses on the forest

floor. Moss is the crucial element. The amount of nitrogen coming from the canopy

depends on trees having mosses. Many trees don't start to accumulate mosses until

they're more than 100 years old. So it's really the density of very large old trees that

are draped in moss that is important at a forest stand level.

- Direct Solar Fuels

Cyanobacteria are bacteria that produce and secrete fatty acids, which can then

be used for bio fuel feed stocks. Scientists are working to harness this process using

only the essential elements required to generate the fatty acids for harvest. These

elements are water, sunlight, and CO2. This innovative path to biofuel development

shortens the process and is predicted to yield upwards of 10 times the usable energy

of conventional biofuels.

This cyanobacteria is being modified genetically so that it can produce optimized

yields of C-16 and C-18 lipids (i.e., fats). These lipids will be used as a feed stock to

a process that will convert the lipid feedstock into a biodiesel fuel. The genome of

this bacteria is completely sequenced, and it is much better suited to metabolic

engineering than eukaryotic algae

. The cyanobacterium is photosynthetic and fixes CO2 into a feed of carbon

molecules, and the Shewanella baterium converts that feedstock into longer

hydrogen molecules, usable as a second feedstock, which can then be refined into a

commercially viable bio fuel. The breakthrough that makes the hydrocarbon-

generating process possible is a special latex developed by BioCee, Inc. This latex

lines the bioreactors where the bacteria can live stably, free to produce

hydrocarbons. Pilot industrial production trials have not been announced to date.

What is exciting about the whole process is that it requires only sunlight and CO2 to

fuel it. This is an elegant and innovative way to generate renewable hydrocarbon bio

fuels in a way that bypasses the hundreds of millions of years needed for fossil fuels

to form, using only the sun and air to fuel the process.

- Make Bio-PlasticsButanediol (BDO) is an intermediate chemical compound used to make a wide

array of useful products. The range of products includes car bumpers, spandex,

elastic fibers, and polyurethanes, to name a few. World production is about 1 million

metric tons each year for  1,4-butanediol (OH groups on the first and fourth position

of the butane carbon chain). Scale up of this bio-plastic process looks promising,

because E. coli is already being successfully grown commercially in large tanks for

growing food stuffs. The appeal of this process goes well beyond its novelty.

Conventional industrial processes for making 1,4-butanediol are very energy intense

and use butane gas, phosphoric acid, acetylene, and formaldehyde, as well as

esters and anhydrides of maleic and succinic acids in an alternative process.

- Oil Spill Clean-Up

A certain strain of  bacteria Pseudomonas aeruginosa called NY3 has been

discovered, which can help clean up oil spills.. The NY3 strain of this bacteria has an

extraordinary ability to produce a group of biosurfactants called rhamnolipids. These

rhamnolipids have the capacity to break down oil and degrade toxic PHAs (polycyclic

aromatic hydrocarbons) in the oil. Strains of the NY3 bacteria have been developed

to produce high yields of 12 grams per liter. This opens the way for rapid scale-up in

the near future. Conventional oil spill clean-up chemicals are often found to be toxic.

Rhamnolipids are both biodegradable and non-toxic.

Bacteria can turn a number of toxic substances into non-toxic ones; this process

is referred to as “biodegradation.” Biodegradation is an area of active research in

marine ecology. There are several types of bacteria that live in the ocean and eat oil

petroleum hydrocarbons from oil tanker spills. Some research has found that adding

other nutrients to oil spills can speed up the growth of bacteria at the spill and

therefore speed the “removal” of the oil by the bacteria. Other types of bacteria can

biodegrade cyanide. Cyanide is a by product of plastics manufacture, aluminum

processing, and is contained in cigarette smoke. Inhaling cyanide gas can cause

poisoning including long-term heart and brain damage, and death. Certain soil

bacteria can turn cyanide into harmless carbon dioxide or ammonia.

Bioremediation involves using biological organisms like bacteria to solve an

environmental problem such as contaminated soil or groundwater. Bacteria and

other microbes are constantly breaking down organic matter. When their habitat

becomes polluted, some microbes die while others that are capable of eating the

pollutant may survive. Bioremediation works by giving these microbes nutrients,

oxygen, and any other conditions that would encourage their rapid growth.Cleaning

oil spills with marine bacteria is one type of bioremediation.

Bioremediation does not work for all types of pollution. For example, sites where

chemicals are found at too high of a concentration will kill most microbes. However,

bioremediation does provide a technique for cleaning up pollution by enhancing the

same processes that occur in nature. Bioremediation can be safer and less

expensive than other methods such as burning or burying contaminated.

REFERENCES

Molles, Manuel C. 2010 Ecology, Concepts And Applications, International Edition,(5th Edition), McGraw-Hill

Clifton, C. E. Introduction to Bacterial Physiology. New York, 1997.

Gunsalus, I. C, and R. J. Stanier. The Bacteria, vols. 1–5. New York, 2001.

Stanier, R. J., M. Doudoroff, and E. A. Adelberg. The Microbial World, 2nd ed. New

York, 2003