Enzymatic degradation of carbaryl by pseudomonas cepacia and isolation of a plasmid responsible for degradation

摘要

The increased use of various types of pesticides in agriculature has led to much greater emphasis on the possibility of serious environmental contamination arising from their use. Although pesticides are deliberately designed to alter the balance of ecology, that is to eliminate or restrict undesirable species in favour of species considered desirable for man's continued existence but the ubiquotous nature of so many biological and biochemical processes makes in unlikely that even highly specific pesticides will not affect some other biosystems. Some of these chemical persist for longer times in soil and water, however, these do get degraded naturally by a number of means. But it is needed that these pesticides be degraded in an accelerated manner which can be attained by biological means using acclimated microorganism. In the present study, a soil bacterium, Pseudomonas cepacia was isolated which efficiently degraded carbaryl in laboratory and soil environment. It could degrade 70 percent of added carbaryl in just 4 days and degradation was completed by 16~(th) day in the soil. The enzymatic nature of degradation was established and conditions for production of enzyme were optimised. The enzyme was maximally produced in Synthetic medium in presence of carbaryl (200 mu g.ml~(-1)) as sole `carbon'source in stationary phase (72h) under shaking conditions at 37 deg C and pH 7.0. The enzyme was purified and had a molecular weight of 60250 daltons. The genetic basis of degradation was worked out by isolating a plasmid of 42Kb that was responsible for the degradation of carbaryl and the loss of plasmid resulted in the inability of P. cepacia to degrade carbaryl. The organism or its cell free extracts could be used for detoxification or remediation of soil and water contaminated with carbaryl or related carbamates.