Effects Of Three New Pesticides On Bacterial Community Of Soil And Isolation Of Degrading Bacteria

New pesticides have become the first choice with the traditional pesticides being banned. The new pesticides have advantages of high activity, low toxicity and less dosage, compared with conventional pesticides. However, only a small amount of the pesticide functions against the target organisms, and most of the pesticide remains in the soil, which caused severe destruction of the ecological environment. At present, the researches on isolation and selection of new pesticide-degrading bacteria, as well as their biodegradation capacity of microbial and degradation mechanism are still at primary stage. Isolating bacteria capable of degrading new pesticides from soil and analyzing their degradation effect could be very important by providing a theoretical basis for controlling environmental pollution and developing green agriculture.The effects of pesticide quizalofop-p-ethyl, fipronil and fomesafen on bacterial community in the soil were respectively analyzed using the technique of PCR-DGGE. The results indicated that the soil bacterial community structures were significantly changed after treatment. The bacterial diversity of soil decreased first after application of quizalofop-p-ethyl, and then increased. But it increased after treatment of fipronil and fomesafen then descreased. According to the sequencing results of bands in DGGE profiles, it was inferred that members of bacterial genera had tolerance and the potential of degradation to quizalofop-p-ethyl, fipronil and fomesafen respectively. These microbial groups could be used as the indigenous microbial resources that can reduce pesticide residues to isolate and screen.Naturally occurring bacteria isolates capable of metabolizing pesticides have received considerable attention because they offer the possibility of both environment friendly and in situ detoxification. In this study, DIG labeled probes had been synthesized based on the sequencing results of bands in the DGGE profiles, and purposefully selected degradation strains from soil, combining colony in situ hybridization technique in the modern molecular biology with the conventional plate culture method. One strain capable of biodegrading quizalofop-p-ethyl was isolated from soil, and named L1. The strain was identified as Pseudomonas sp., based on morphology, physio-biochemical identification and the phylogenetic analysis of16S rRNA. The strain L1was able to utilize quizalofop-p-ethyl as the sole source of carbon, and the quizalofop-p-ethyl content decreased by almost50%after7days. This result provided a basis for future research on degradation mechanism and functional genes.