Abstract
Microbial bioremediation especially bacterial bioremediation is now gradually gaining global attention as a potential, less harmful, ecofriendly and economically viable method to decontaminate/detoxify polluted environments. Soil, the naturally occurring critical zone of the earth's surface made up of various unconsolidated mineral and organic materials, is a niche for the inhabiting soil microflora. This microflora in the soil environment is the most abundant (aerobic and anaerobic) culturable microbial population (of size more than 108 cells/g soil) with rich diversity. These organisms possess the ability to undergo natural process of evolutionary genetic modification for adapt to an abiotically and/or biotically altered environment. Due to the unabated anthropogenic and industrial activities due to the growing urbanisation and industrialisation, the soil gets repeatedly contaminated with various toxic and xenobiotic compounds, including heavy metals, poly aromatic hydrocarbons, pesticides, oil spillage, nuclear and radioactive wastes, etc. The inhabiting soil bacteria in such contaminated sites would have developed tolerance capacity towards various hazardous compounds possibly through genetic modification for their survival through generations. These could be potential agents for in situ and ex situ bioremediation applications. The phenomena of bacterial bioremediation involve multiple physicochemical mechanisms, such as, cell surface adsorption, intracellular absorption/accumulation, chemical binding on cell surface, entrapment in the porous cell matrix, encapsulation, precipitation, oxidation-reduction, etc. for efficient removal/biodegradation of the toxic compounds. This chapter attempts to summarize the various scientific findings in recent times regarding the in situ and ex situ application of various soil bacteria in bioremediation of toxic wastes and contaminated environments.