Some of the major beneficial activities of bacteria are as follows:
Role in Nature:
1. Nature’s Scavengers:
Bacteria decompose organic matter, by decay and putrefaction, to keep our earth clean.
Decay is the aerobic decomposition of organic matter without the release of foul smell, while putrefaction is the anaerobic decomposition of organic compounds with the release of foul smell (NH3, H2S, and CH4).
2. Control of Pollution:
Acetobacter aerogens is known to decompose DDT. Peudomonas decomposes petroleum wastes and other man-made pollutants. Recentlyinbioremediauon technology, naturally or genetically modified bacteria are released to remove pollutants like heavy metals, dyes, pesticides, petroleum wastes, coal wastes etc. from environment. The purity of Ganga water is due to Bellovibrio bacteriovorous.
3. Disposal of Sewage and Agro-wastes:
Sewage is the household and industrial waste water discharges. Bacteria decompose organic wastes of wage and agriculture into humus which can improve soil fertility.
4. Symbiosis:
Symbiotic bacteria present in the rumen (1st chamber of stomach) of herbivore help in cellulose digestion. In human colon E. coli synthesize vitamins B and K.
5. Material Cycling:
Many bacteria and saprophytic fungi decompose dead organism- so that complex organic matter convert into simpler organic matter and subsequently into inorganic components which can be reused to make the living matter. Therefore, bacteria regulate biogeochemical cycles for C, H, S, P etc.
Role in Agriculture:
6. Gobargas (biogas):
In gobar gas plant bacteria can be used for production of methane (fuel gas) by anaerobic breakdown or fermentation on cow dung, animal wastes etc.
7. Ensilage:
It is a preserved cattle feed or fodder prepared by bacterial activity.
8. Soil Fertility:
Some bacteria increase the soil fertility and acts as a Nature’s farmers. These bacteria involved in the decomposition and transformation of nitrogenous organic compounds maintenance of soil fertility. These are of three types-ammonifying bacteria, nitrifying bacteria, nitrogen fixing bacteria.
(a) Ammonifying bacteria:
These bacteria release ammonia from protein, e.g. Bacillus vulgaris, B. ramosus etc. Soil ammonia trapped in form of ammonium salts, and available for plant absorption.
(b) Nitrifying bacteria:
The soils contain two types of nitrifying bacteria: Nitrite bacteria which convert ammonium nitrogen into nitrites (e.g., Nitrosomonas, Nitrosococcus), and Nitrate bacteria which convert nitrites into nitrates (e.g., Nitrocystis) the most readily utilized of all nitrogen compounds by green plants.
(c) Nitrogen fixing bacteria:
Nitrogen fixation is the conversion of free atmospheric dinitrogen (N2) into compounds of nitrogen. Bacteria and Cyanobacteria carry out 60% of total nitrogen fixation in natural ecosystems. For example, Azotobacter chroococcum, Beijerinckia and Clostridium pasteurianum occur as saprophyte in soil. Rhizobium leguminosarum (syn. Bacillus radicicola) and related species live inside the root nodules of leguminous plants as symbionts and fix atmospheric nitrogen.
9. Biopesticides:
Biopesticides are derived from such natural materials as bacteria, animals, plants, their genes or metabolites and certain minerals that are used to protect vegetation against damaging pests. Bacillus subtilis (strain QST 713) controls the growth of certain harmful bacteria and fungi that cause scab, powdery mildew, sour rot, downy mildew, and early leaf spot, early blight, late blight, bacterial spot, and walnut blight diseases through competition. Bacillus sphaericus (strain 2362) acts as an endotoxin to mosquito larvae of Culex, Psorophora and Anopheles species, when the larvae consume the live bacteria. Bacillus thuringiensis (Bt) is an aerobic spore forming bacterium.
Different varieties of this bacterium contain plasmids for synthesis of several Insecticide Crystal Protein (ICP) toxins viz., a – β & endotoxins.Now transgenic plants produced through introduction of endotoxin genes of Bt. Agrobacterium radiobacter (strain K84) occurs in soil and near plant roots. When used as a pesticide active ingredient, it releases a protein that inhibits the growth of A. tumefaciens that causes crown gall disease in plants, by competing directly with A. tumefaciens for food and space.
Role in Industries:
10. Fiber retting:
Retting is a process by which commercial plant fibers like jute, flax, hemp etc. are separated by the bacterial decomposition of pectin substances that hold the fibers together. In anaerobic retting, fibrous plant body immersed in water tanks where butyric acid bacteria (Clostridium butylicum) decompose the middle lamella and separate the fibers. In dew retting, periodic sprinkling of water is done and Pseudomon as fluorescence does the retting process.
11. Leather industry (Tannery):
In leather industry, removal of hairs, fats and other tissues from rawhide is done by bacteria. The cleaned hides are then tanned to prepare leather.
12. Curing:
It is the removal of bitterness and to give unique flavor and aroma in tea, coffee, tobacco and coca, e.g., Bacillus megatherium, Micrococcus candidans.
13. Biodegradable plastics are prepared from the PHB (Poly β-hydroxybutyrate) that act as reserve fatty acid in bacteria.
14. Dairy Products:
A variety of dairy products are prepared due to fermentation of milk. Lactic acid bacteria convert lactose (milk sugar) to lactic acid which helps in curdling of milk protein casein. Mixed Fermentation of milk by lactic acid bacteria and yeasts produce kefir and kumiss (mild alcoholic beverage). Large holes of Swiss cheese are formed due to release of large amount of CO2 by Propionibacterium sharmanii.
Pasteurization:
It is the heating of milk at 62.8 C for 30 min of 71.6°C for 15 sec. and sudden cooling at4-5°C to kill the non-spore forming bacteria. It is used for preservation of milk.
15. Bioleaching or bio-mining:
Bacteria are used to recover metals like nickel, lead, zinc, copper etc. from low grade ores which otherwise can’t be economical. Precious metals like Gold and silver obtained through bioleaching of pyrite ore and iron sulfide respectively.
16. Production of lactic acid, acetic acid, acetone, butanol, N-butanol, alcohol, glycerol etc.
17. Production of Antibiotics:
Antibiotics are the biochemicals (secondary meta-bolites) produced by micro-organisms and are capable of inhibiting the growth of pathogenic microorganisms. The phenomenon of growth inhibition by antibiotics is called antibiosis. Alexander Flemming (1929) discovered the first commercial antibiotic penicillin from Penicillium notatum (a fungus). But, Waksman (1942) coined the term of antibiotics. At present, about 7,000 antibiotics have been discovered. Some of them produced by bacteria are as follows.
Ernest Chain and Howard Florey established the antibiotic potential of penicillin. At present, about 7000 antibiotics are known and every year about 300 new antibiotics are discovered. Some of them produced by bacteria are as follows.
18. Production of Vaccines:
A vaccine is a suspension of killed, or living but inactivated bacteria which, when inoculated into the body, act as antigen causing development of antibodies that render the body immune or at least, resistant to infection by bacterium. It was with Bacillus anthracis that the first systematic vaccination was conducted.
19. Thermostable Enzyme.
A thermostable DNA polymerase called Taq polymerase is isolated from a bacterium Thermus aquaticus which is used in PCR (polymerase chain Reaction) for amplification of gene of interest.
20. Transgenic Bacteria:
These are genetically engineered bacteria whose normal genome has been altered by introduction of a foreign gene (transgene). Trangenic Escherichia coli are cultured to extract human insulin.
21. SCP (Single cell protein):
It is the production of microbial biomass (e.g. bacterium, yeast) on a commercial scale in a fermentor, dried and sold as alternate sources of proteins for human and animal nutrition.
The common SCP are:
i. Bacteria – Methylophilus methylotrophus, Rhodopseudomonas capsulata etc.
ii. Cyanobacteria – Spirulina
iii. Algae – Chlorella
iv. Yeasts – S. cerevisiae, Candida utilis etc.
v. Filamentous fungi – Fusarium graminearum
The eukaryotic SCP has less nucleic acid content than prokaryotic and is therefore more suitable for human consumption, since excess nucleic acid causes health problem.