In
Agriculture: Soil Fertility
Nitrogen is essential for plants for the synthesis of
protein, nucleic acids, and other nitrogen containing compounds. Molecular
nitrogen (N2) occupies almost 80% of the atmosphere. For use by plants nitrogen
must be fixed (combined) with other elements such as oxygen and hydrogen. The
plants take nitrogen in the from of nitrates. In soil, nitrates are formed by
the activity of bacteria by two processes:
(i)
By nitrogen-fixing bacteria : Nitrogen-fixing bacteria are found in the
soil either freely e.g., Azotobacter, Clostridium or in root nodules of
leguminous plant e.g., Bradyrhizobium, Rhizobium leguminosarum. These bacteria
are capable of converting atmospheric free nitrogen into nitrates, the
compounds which are useful for the growth of plants. The nitrogen fixing
bacteria are the natural fertilizers of the soil. Because of their ability of
fixing the atmospheric nitrogen, the leguminous plants are commonly used in
crop rotation.
(ii)
By nitrifying bacteria : The decay of plant and animal proteins, affected
by saprophytic soil bacteria, returns nitrogen to the soil in the form of
ammonia. The process is termed ammonification. The ammonia is not readily
utilized by plants. The ammonia so produced, reacts with the soil water to form
ammonium hydroxide (NH4OH), which in turn, reacts with various
chemical substances found in the soil, to form ammonium salts.
In the process of nitrification, the
nitrifying bacteria convert the ammonia or ammonium salts to nitrate, available
as the principal nitrogen source for green plants.
Thus, the ammonifying and nitrifying bacteria maintain he supply of nitrate to the soil
Disposal of Sewage
Sewage
contain domestic wastes, human wastes, leaves of plants, industrial wastes and
organic food wastes, etc.During the anaerobic phase of decomposition of sewage
wastes, methane (CH4) and CO2 are produced by
methanogenic bacteria, such as, Methanococcus and Methanobacterium etc. From
these gases, methane is used as a biogas as fuel and CO2
is used by some algae, present in the tank for photosynthesis. The oxygen,
produced as a result of photosynthesis, is used for the respiration of living
organisms of sewage.
The sludge, that contains harmless organic and inorganic
materials, and microorganisms can be dried and used as the fertilizers.
In dairy
Through their metabolic activities,
bacteria may play important roles in the manufacture of curd, butter and
certain kinds of cheese from milk.
Streptococcus lactis and
Lactobacillus lactis, etc. are found in milk. These bacteria ferment lactose
sugar found in milk to form lactic acid, by which milk becomes sour. If the
milk is heated at 62.8° C for 30 minutes and is simultaneously cooled, the
number of lactic acid bacteria is reduced, but all the spores and cells of
these bacteria are not destroyed but pathogenic spores are destroyed. In this
way, though the milk becomes sour, but it takes longer time to become sour than
ordinary milk. This process is known as pasteurization
The manufacture of almost all milk
products, such as curd, butter, cheese, ghee is based on the bacterial
activity. Lactic acid bacteria bring together droplets of casein, a protein
fund in milk and help in the formation of curd. On churning of curd, butter is
derived in the form of fat's rounded droplets. The butter on heating is
converted into "ghee".
Following bacteria are responsible for dairy product—
Curd
|
Streptococcus lactis
|
Cheese
|
Lactobacillus lactis
|
Butter
|
Streptococcus lactis
|
Yoghurt
|
Lactobacillus vulgaricus
|
Buttermilk
|
S. lactis and S. cremoris
|
Industrial
value
In Vinegar industry :
The
commercial production of vinegar (acetic acid) involves bacterial action. In
the first step, the carbohydrates undergo fermentation to be converted into
ethyl alcohol (C2H5OH) through the action of yeasts. In the second step, the aerobic
bacteria e.g., Acetobacter aceti and Mycoderma aceti, oxidize the alcohol to
acetic acid.
In tobacco industry :
Bacillus
megatherium and Mycrococcus candidans is used for its fermentative capacity for
developing flavour and taste in tobacco leaves.
In tea industry :
By
fermentative action of Mycrococcus candidans, the curing of tea leaves is done.
By this process special flavour and the taste is developed in the tea leaves.
Tanning of skin to produce leather :
Some
bacteria by fermentation decompose fats, which are found in skin of animals,
with the result that skin and hair are separated from each other and thus
leather becomes ready for use.
Role
of Bacteria in Genetic Analysis
Bacteria
are very useful organisms for genetic analysis. Under favourable conditions of
growth and reproduction, some bacteria (such as E.coli) divide after every 20
minutes, the progeny of each division becomes a new generation. A genetic
experiment can be completed with bacteria in hours, while an analogous experiment
with a multicellular organism would take months or years to be completed
because the generation time of such organisms are moths or even years in
duration.
Role
of Bacteria in the Production of Antibiotics (medicines)
An
antibiotic (the wonder drugs of today) is a chemical, that is produced by a
living organism and is capable of inhibiting the growth of pathogenic
microorganisms. Some of the antibiotics are produced by bacteria. Man has
isolated many of the antibiotics from various bacteria and has utilized them as
drugs for the treatment of diseases caused by the pathogenic organisms e.g.,
Bacillus brevis produces antibiotic thyrothricin and B. subtilis produces
antibiotic subtelin. One of the best known antibiotic is the penicillin,
obtained from the mold Penicillium notatum, was discovered by the British
bacteriologist Alexander Fleming in 1928.
The
antibiotics are not laboratory chemicals as are the antiseptics or
disinfectants. In some cases antibiotics have been synthesised by chemist in
the laboratory, in which case they are known as chemotherapeutic agents.
