Importance of Bacteria:
1. Agriculture:
Many species of saprophytic and symbiotic bacteria add to the fertility of the soil and provide nitrogen to the plants.
i. Ammonifying Bacteria: Bacillus subtilis, B. mycoides, B.ramosus, etc act upon the dead animal and plant tissues and decompose their complex organic compounds like proteins into ammonium compounds. They are also known as putrefying bacteria.
ii. Nitrifying Bacteria: Nitrosomonas oxidize the ammonium compounds into nitrites in presence of free oxygen and Nitrobacter oxidizes nitrites into nitrates in the presence of free oxygen. Thus ammonifying and nitrifying bacteria increase the number of nitrogenous compounds in the soil. Dead plants, animals and dung, etc are converted into humans by the action of putrefying bacteria. These humans themselves act as fertilizer for plants.
iii. Nitrogen Fixing Bacteria: They are Azotobacter, Clostridium, and Rhizobium spp. They fix the free nitrogen in the soil and make it available to the plants. The first two bacteria live freely in the soil and fix the atmospheric nitrogen in the form of nitrogenous compounds in the soil. The third one is a symbiotic type. They live in the root nodules of leguminous plants and take the free atmosphere nitrogenous fertilizers available. The leguminous plants make the soil rich in nitrogen and are therefore used as green manures.
2. Industry:
A large number of saprophytic bacteria are employed in the manufacture of various industrial products.
i. Butter-making industry: Saprophytic bacteria such as Lacto Bacilli popularly known as starters make the milk sour and produce various flavors. These bacteria are largely employed in the butter industry for ripening milk and producing flavors in butter.
ii. Cheese-making industry: Bacteria are employed in this industry. First, the casein of milk is coagulated and then it is ripened by certain bacteria. The bacteria make the casein spongy, and soft and give it characteristic taste and flavor.
iii. Vinegar-making industry: Bacillus acetic converts the sugar solution into vinegar.
iv. Alcohol and Acetone Manufacture: Butyl alcohol and acetone are manufactured by the action of bacteria on molasses.
v. Tobacco curing: Crude dry tobacco leaves pass through curing and ripening processes before they are ready for use. bacteria are employed in both these processes and the peculiar taste and smell in the tobacco is due to the bacterial activity. For this purpose molasses and alcohol are added to tobacco.
vi. Tea curing: Crude teal leaves are acted upon by certain bacteria. The process is known as curing which is employed to impart a peculiar taste and flavor to the leaves. For this purpose, alcohol is added to tea leaves.
vii. Leather tanning: The hides and skins after drying, salting, and clearing are steeped in fluids containing specific bacteria. The process of fermentation goes on for some time and then they are transferred to tan pits and are further allowed to be fermented. This whole process is known as tanning and the bacteria employed in the process are obtained from cow dung and the excreta of dogs and poultry.
viii. Fibre retting: Retting is the process of separating fibers from plant tissues. Bacteria employed in this industry, cause decay of the softer tissues and tender fibers easily separable mechanically. Fibers of flax, hemp, jute, coconut, and other fibrous plants are obtained by immersing the specific plant organs in stagnant pond water where bacteria develop and cause retting.
ix. Sewage Work: In order to remove solid and semi-solid constituents of sewage it is allowed to putrify. Putrefying bacteria are allowed to act upon sewage under anaerobic conditions. It gets decayed and liquified. It is now filtered and the liquid is either drained out to the river or used as manure in fields. For this purpose, in the soak pits the horse dung is filled up.
x. Ensilage: It is the process of preserving green fodder in pits. Certain bacteria help in the preservation of fodder.
xi. Medicines: Antioxins are the chemical substances produced in the host tissues in response to the attack of parasitic bacteria. Different vaccines and serums now prepared from these antitoxins are used in the treatment of specific ailments. The antibiotics such as streptomycin, aureomycin, chloromycetin, etc are obtained from certain actinomycetous bacteria.