A wide variety of contaminants have been introduced in the environment by anthropogenic activities or natural processes. Pollution not only affects humans but also severely hampers the ecosystem by destroying habitats of the affected flora and fauna. In addition, a variety of environments such as subsurface aquifers, oceans, anoxic soils, sediments and soda lakes have been affected. Contaminants such as polycyclic aromatic hydrocarbons (PAHs) are of significance as they have been identified as mutagenic, carcinogenic and teratogenic.

Methods such as use of dispersants, solvent mixtures and detergents have been employed for the clean-up of the affected sites. These chemicals may be useful in the short-term but they significantly affect the surviving organisms and alter the food-chain of the ecosystem. In addition, they don’t necessarily destroy and may mobilize contaminants. In recent years, focus has shifted towards natural processes for degradation of contaminants. Bacteria can be employed for successful, sustainable and harmless clean up of such contaminated environments. Attenuation of pollutants including hydrocarbons such as PAHs can be achieved under aerobic conditions by intrinsic bacteria present in the impacted site or by introduction of organisms capable of biodegradation. Few studies have investigated the degradation potential and mechanisms of bacteria in anoxic, saline and alkaline conditions.