Microorganisms play several key roles in the
environment. Besides their, well-known activities
in biogeochemical cycling, soil fertility maintenance
etc., several microbes could be shown very helpful
in maintenance of environmental quality through
biodegradation of wastes (urban, municipal and
industrial) into useful products and also in
biodegradation ofharmful pesticides used in
crop protection and public health. DOT, lindane
heptachlor, chlordane, malathion etc., are biodegraded
by several bacteria, and fungi. These microbes
are thus efficient purifiers of the environment.
The use of mycorrhizae to enhance the
uptake of nutrients and water for establishment
of seedlings on degraded lands. This will, however,
not lead to the improvement of soil fertility
by mycorrhizae as such, although the success
of plant growth will eventually lead to reclamation
of degraded lands. However, nitrogen fixing
bacteria like Rhizobium or actionomycete
genus Frankia can be used to induce nodule formation
in a variety of plant species, so that these
can be used for improving soil fertility of
degraded lands. This nodule formation can be
induced, both in leguminous and non-leguminous
plant species comprising annuals (cereal and
legume crops) and perennials (trees). Efforts
are underway to manipulate the genes of both
host and rhizobia to obtain maximum
efficiency of nodule formation. Strains are
also being tailored for unusual soil environments
representing degraded lands.
Besides this, microbes are also able to remove
toxic heavy metals from industrial wastes. Some
bacteria are also able to metabolize hydrocarbons
in the petroleum and thus very useful in removal
of oil-spills and grease from water bodies.
A strain of Pseudomonas aeruginosa
has been developed in USA which is able to produce
a glycolipid emulsifier that reduces the surface
tension of an oil- water interface, thus removing
oil from water. For removal of grease deposits,
a mixture of several bacteria is used.
Some microorganisms can also be used in environmental
monitoring and biomonitoring. Environmental
pollutants can be detected by the use of appropriate
strains of microbes as biosensors. Biosensor
is a biophysical device used to detect the presence
and quantify the specific substances (sugars,
proteins, hormones, pollutants) in the specific
environments.
Soil Fertility
Microbes are being exploited in two important
ways - biofertilisers, and for creating new
nitrogen-fixing organisms.
Biofertilisers Potential of Rhizobium, Azotobacter,
Beijerinckia, and Azospirillum, Cyanobacteria,
such as species of Aulosira, Anabaena, Nostoc,
Plectonema, Scytonema, Tolypothrix, and
Azalia as biofertilisers has been exploited
so as these could serve as an alternative to
chemical fertilizers.
Many brands of rhizobial inoculants are already
in market today in the country. Several organization
and manufacturers are producing huge quantities
of Rhizobium culture in the country.
These includes Micro Bac., India, Shyam nagar,
Parganas; Bacifil Inoculants, Lucknow; Govt.
of TamilNadu; Nitro Fix Industries, Calcutta
(W. Bengal) and Indian Organic Chemical Ltd.
Bombay. In some other States, units are being
prepared for increase in its production. Much
progress has also been made with cyanobacteria
in this direction. Mycorrhizae, both ecto and
endomycorrhiza help in uptake of N, P, K and
Ca. They, particularly help in phosphorous nutrition.
Biopesticides
Several microbes (viruses bacteria and fungi)
are being developed as suitable biopesticides
for the management of insect and nematodal pests.
Some fungi have good potential of their use
as bionematicides to control nematodal pests
of vegetables, fruit and cereal crops. Some
bacterial and fungal products are also in use
to control diseases of roots and shoots of plants.
Nitrogen Fixers
Through recombinant DNA technology efforts
have been made to introduce nitrogen-fixing
genes (nif genes) into wheat, corn, rice, etc.
Plasmids of the bacterium, E. coli
and yeast are being worked out for such a possibility.
Hybrid E.coli plasmid cloned with nif
genes of a nitrogenfixing bacterium, Klebsiella
pneumoniae and hybrid yeast plasmids are
then integrated.
