Characterization and regulation of catabolic genes

Although a wide range of microorganisms have been discovered that are able to degrade highly stable, toxic xenobiotics, still many pollutants persist in the environment. Recent advances in the field of r-DNA technology has pr ovided solutions to these problems. One important factor limiting the biore mediation of sites contaminated with certain hazardous wastes is the slow r ate of degradation. This slow rate limits the practicality of using bacteri a in remediating contaminated sites. It is possible to extend the range of substrates that an organism can utilize. It is even possible to endow an or ganism with the ability to degrade a predetermined range of xenobiotics. Be cause biotechnological processes are based on natural activities of microor ganisms and costitute variations in classic domestic waste treatment proces ses, they are publicly more accepted. This is an area where genetic enginee ring can make a marked improvement by manipulating catabolic genes of micro organisms. Advances in r-DNA technology have opend up new avenues to move t oward the goal of genetically engineered microorganisms to function as "des igner biocatalysts" in which certain desirable biodegradation pathways or e nzymes from different organisms are brought together in a single host with the aim of performing specific detoxification. In the last 2 decades much p rogress has been made in this direction, and as a result catabolic genes ha ve been cloned and characterized for organochlorines, polychlorinatedbiphen yls, chlrobenzoates, naphthalene etc. The aim of this review is to provide an insight in the recent advances made on characterization and expression o f catabolic genes that encode the degradation /detoxification of these pesi stent and toxic xenobiotic compounds.