Importance of bacteria

Harmful effects

• Bacteria are agents of disease of animals and plants such as syphilis, cholera, tetanus
• Bacteria cause milk and food deteriorate
• Denitrifying bacteria such as Thiobacillus lead to deterioration of soil fertility.

Useful effects

• Saprotrophic bacteria cause decay of waste materials and lead to formation of humus and recycling of minerals. E.g. Bacteria (Nitrosomonas and nitrobacter) convert organically combined nitrogen (e.g. protein) to nitrate which are absorbed by plants.
• Nitrogen fixing bacteria e.g. Azobacter fix nitrogen into the soil.
• Aerobic and anaerobic bacteria are useful in digestion of sewage into harmless substances. Methane gas given off is sometimes used for fuel.
• Mutualistic bacteria in ruminants’ assist ruminants to digest cellulose, and synthesis of vitamin K and B group.
• Some bacteria on the skin of humans enable it to obtain protection again inversion of pathogenic organism
• Bacteria and fungi are useful for making of cheese.
• Used for production of useful chemicals in genetic Engineering such as insulin