Microbial adaptation for pesticide degradation

During the 30 years following the discovery of microbial adaptation for pesticide degradation, there were intermittent reports of the same phenomenon affecting the persistence of other pesticides. However, due to the fact that virtually none of these reports concerned situations where reduced pesticide persistence affected pest control efficacy, microbial adaptation for pesticide degradation was largely relegated to the status of academic curiosity. In fact,... 

The research efforts that have been stimulated by the phenomenon of enhanced degradation have resulted in the creation of a substantial knowledge base regarding microbial adaptation for pesticide degradation and associated pest control failures. The body of scientific literature on the subject has grown rapidly and Is now substantial. Recent reviews of enhanced degradation and microbial adaptation for pesticide degradation by Kaufman (2) (59 ref.),... 

By the mid 1970 s, the replacement of these materials with degradable, soil-applied pesticides In nearly all markets set the scene for the development of current Interest In adapted microbial pesticide degradation. 

The exact mechanisms for microbial adaptation to the pesticide molecule in soils that develop enhanced degradation capacity are not completely understood. These processes could be viewed from the ecological and population aspects, from their biochemical and enzymatic reactions, or from the genetic aspects, in which extrachromosomal elements may be involved as part of the process. 

In addition to the amount of pesticide present, the degradation rate could be affected by the availability of the chemical for degradation. Ogram et al. (30) have recently presented evidence suggesting that only the 2,4-D (2,4-dichloro phenoxyacetic acid) in soil solution, but not that adsorbed on soil colloids, could be degraded by soil microbes both in soil solution and sorbed on soil colloids. Other considerations should also be given to the nature and quantity of soil microbial biomass present in relation to nutrient availability (26,28,31) and the adaptability of microbes, either by natural selection or by genetic manipulation, to attack and utilize the pesticide chemical (32). 

Several mechanisms have been proposed to explain how a soil microbial population becomes adapted to a particular pesticide to result in enhanced degradation and also to explain how this ability can be retained for months and even years without further pesticide applications. Although a discussion of this subject is considered beyond the scope of this paper, the topic has been extensively reviewed 3, 4, 3j), 40j. ... 

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