Microbial degradation of xenobiotics in the environment

Biodegradation of naturally occurring organic compounds follows their synthesis. In contrast, man-made compounds, also known as xenobiotics, are often refractory to degradation. The main reason is that they cannot be recognized by naturally present organisms and therefore do not enter common metabolic pathways. The physical and chemical characteristics of the compounds, as well as environmental factors, may influence their biodegradability. Some compounds may be transformed only in the presence of another compound which appears as a carbon and energy source. Very often compounds are degraded sequentially through the activity of a series of different organisms. The main degraders in nature are microorganisms, mostly bacteria and some fungi. These organisms, due to their rapid rates of multiplication and great metabolic potential, are able to adapt to new substrates. Selection of degradative potent microorganisms and their successive adaptation to a naturally persistent compound might be a powerful means for environmental detoxification. Although numerous laboratory experiments have given positive results, very few are applicable on a large scale. It is necessary to select microorganisms or microbial communities capable of controlled degradation of persistent organic chemicals without their transformation to other, more hazardous compounds. Better understanding of metabolic pathways for the biodegradation of specific organic compounds as well as more thorough knowledge of degrading microorganisms will make purposeful application of biodegradation possible.