Pesticide degrading microorganisms

The rate and extent of pesticide metaboHsm can vary dramatically, depending on chemical stmcture, the number of specific pesticide-degrading microorganisms present and their affinity for the pesticide, and environmental parameters. The extent of metaboHsm can vary from relatively minor transformations which do not significantly alter the chemical or toxicological properties of the pesticide, to mineralisation, ie, degradation to CO2, H2O, NH" 4, Cf, etc. The rate of metaboHsm can vary from extremely slow (half-life of years) to rapid (half-life of days). 

For those pesticides that are cometabolized, ie, not utilized as a growth substrate, the assumption of first-order kinetics is appropriate. The more accurate kinetic expression is actually pseudo-first-order kinetics, where the rate is dependent on both the pesticide concentration and the numbers of pesticide-degrading microorganisms. However, because of the difficulties in enumerating pesticide-transforming microorganisms, first-order rate constants, or half-hves, are typically reported. Based on kinetic constants, it is possible to rank the relative persistence of pesticides. Pesticides with half-hves of <10 days are considered to be relatively nonpersistent pesticides with half-hves of >100 days are considered to be relatively persistent. 

Approximately 100 strains of pesticide-degrading microorganisms were tested for their ability to degrade... 

Since this early discovery there has been considerable appreciation for the role of the soil microbial community in pesticide transformations. In some cases the role of microorganisms has been stressed by comparison of degradation rates in natural and sterilized systems (32), while in others researchers have chosen to use isolation of pesticide-degrading microorganisms from soil sis evidence of microbial involvement (33). It has also been recognized that environmental conditions that influence microbial activity (temperature, moisture,...) affect the microbial degradation of pesticides in soil (34). The importance of microbial involvement is demonstrated by the many reviews of pesticide/microbe interactions that have appeared (35-41). 

Another major advance has been the isolation of soil microorganisms involved in enhanced pesticide degradation and elucidation of the catabolic nature of the adaptation involved. A partial listing of pesticide-degrading microorganisms that have been Isolated from soil and the principal compound metabolized is shown below ... 

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