Microbes play an important role in agriculture as bio control agents and bio fertilizers. Microbes play a vital role in the cycling of elements like carbon, nitrogen, oxygen, sulphur and phosphorus.

1. Microbes as bio control agents Microorganisms used for controlling harmful or pathogenic organisms and pests of plants are called as bio control agents (Bio pesticides). Bacillus thuringiensis (Bt) is a species of bacteria that produces a protein called as ‘cry’ protein. This protein is toxic to the insect larva and kills them.

2. Microbes as bio fertilizers Microorganisms which enrich the soil with nutrients are called as bio fertilizers. Bacteria, cyanobacteria and fungi are the main sources of bio fertilizers. This is done by microbes either in free living conditions or by having symbiotic relationship with the plants, e.g. Nitrosomonas, Nostoc (free living), symbiotic microbes like Rhizobium, Frankia, mycorrhizae.

Microbes in Industries Microorganisms play an important role in the production of wide variety of valuable products for the welfare of human beings.

1. Production of fermented beverages: Beverages like wine are produced by fermentation of malted cereals and fruits by Saccharomyces cerevisiae.

2. Curing of coffee beans, tea leaves and tobacco leaves: Beans of coffee and cocoa, leaves of tea and tobacco are fermented by the bacteria Bacillus megaterium. This gives the special aroma. 

3. Production of curd: Lactobacillus sp. converts milk to curd. . 

4. Production of organic acids, enzymes and vitamins: Oxalic acid, acetic acid and citric acid are produced by fungus Aspergillus niger. Enzymes like lipases, invertase, proteases, and glucose oxidase are derived from microbes. Yeasts are rich source of vitamin-B complex.