Microbiological and Biotechnological Aspects of Metabolism of Carbamates and Organophosphates

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Abstract
Several carbamate and organophosphate compounds are used to control a wide variety of insect pests, weeds, and disease-transmitting vectors. These chemicals were introduced to replace the recalcitrant and hazardous chlorinated pesticides. Although newly introduced pesticides were considered to be biodegradable, some of them are highly toxic and their residues are found in certain environments. In addition, degradation of some of the carbamates generates metabolites that are also toxic. In general, hydrolysis of the carbamate and organophosphates yields less toxic metabolites compared with the metabolites produced from oxidation. Although microorganisms capable of degrading many of these pesticides have been isolated, knowledge about the biochemical pathways and respective genes involved in the degradation is sparse. Recently, a great deal of interest in the mechanisms of biodegradation of carbamate and organophosphate compounds has been shown because (1) an efficient mineralization of the pesticides used for insect control could eliminate the problems of environmental pollution, (2) a balance between degradation and efficacy of pesticides could result in safer application and effective insect control, and (3) knowledge about the mechanisms of biodegradation could help to deal with situations leading to the generation of toxic metabolites and bioremediation of polluted environments. In addition, advances in genetic engineering and biotechnology offer great potential to exploit the degradative properties of microorganisms in order to develop bioremediation strategies and novel applications such as development of economic plants tolerant to herbicides. In this review, recent advances in the biochemical and genetic aspects of microbial degradation of carbamate and organophosphates are discussed and areas in need of further investigation identified.