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Microorganisms are integral part of our environment and without them the world will not survive. In the final stage of the food chain, microorganisms, including bacteria play the significant role as DECOMPOSERS. They are responsible for breaking down the energy rich organic compounds coming from decayed matter of both plants, animals (including leaves, dead plants and animal bodies or from animal wastes). In short degradation mediated by microorganisms and thus cleaning of environment is termed as bioremedation.

The biosphere is full of microbes and invariably their presence has a strong effect on its surroundings. Microorganisms impart both harmful and beneficial effects on their surrounding environment depending on the microorganisms concerned and also depends on our observation.
The role of microbes in the environment depends on their metabolic activities along with their relations with plants and animals and also on their use in biotechnological procedures and food production.

Role of microbes in nutrient and element cycles
Carbon ©, oxygen (O), hydrogen (H), sulfur (S), nitrogen (N), potassium (K), phosphorus (P), sodium (Na), iron (Fe), magnesium (Mg) and calcium (Ca) are the elemental matters that constitute living system. Among them C, H, O, N, S, and P are the primary components of organic matter. C and H are always present in an organic compound and is represented by the empirical formula for glucose (CH2O). Carbon dioxide (CO2) is taken as an inorganic form of carbon.

Breakdown of complex organic materials to simple forms of carbon, so that other organisms can utilize them, is carried out through biodegradation or decomposition. Interestingly, every organic compounds with natural origin can be broken down into simpler forms of carbon (CO2) with the help of microorganisms and thus returned into the environment. In this scenario compound like plastics, Styrofoam, Teflon, insecticides and pesticides are not so easily broken down by microbes and hence are known as not biodegradable compounds.

Plants and animals can utilize ammonia (NH3), which is produced by conversion of N2 from the atmosphere with the help of microorganisms. This process, known as nitrogen fixation is essential for survival of plants and animals as plants cannot take up free nitrogen from the atmosphere. Nitrogen fixation is the only natural process of replenishing the spent nitrogen from the soil due to agricultural activities. Both free-living (in soil and aquatic environment) and symbiotic bacteria (association with plants) play a major role in nitrogen fixation.

Isolation and study of characteristics of microorganisms responsible for the key biochemical cycles in laboratory cultures are the traditional method for determining their importance in respective cycles. But with the advancement in molecular techniques, the presence of many microorganisms came into light, which could not be detected earlier with isolation technique.

Many hidden microbes with potential beneficial effect on the environment is now uncovered by metagenomic studies followed by laboratory isolation.
The bacterial role in the oxidation of the ammonia need to be reassessed with the invent of this current techniques as now the importance of the group archaea (which cannot be cultured easily in laboratory conditions) also came into light. Metagenomic analysis and [/align] will definitely help us evaluate the role of bacteria and other microbes in the environment in the near future.[align=justify]