51ºÚÁϳԹÏÍø

Abstract

Ethoprophosis an organophosphorus pesticidethat is widely used in agriculture to control major insect pests, has received much concern due to its lethal neurotoxicity and accumulation in soils and groundwaters. Here changes in the bacterial community compositions with 16S rDNA analysis of meta-DNA extracted from 8 group soils with 15-days period (non- treatment, 1-day, 15-day, 30-day, 45-day, 60-day, 75-day, 90-day) during 90 days after treatment with an excessive ethoprophos, organophophorus pesticide was examined. While ethoprophos was degraded actively in soils of from 15days to 60days after treatment, bacterial community of these soils has been rapidly dominated by P roteobacteria phylum, Gammaproteobacteria class, Pseudomonadaceae family, Pseudomonadales order, P esudomonas genus. It was evaluated the rate of degradation by a natural microbial community in each soil after its treatment and found that more ethoprophos was degraded in 30-day soils (50% degradation) and 75-day soils (95% degradation). With the progress of degradation of ethoprophos during 90days after treatment, total composition of the genus Pseudomonas was abruptly increased to 70.1% in 15-day soil from 7.6% of control soils (non-treatment), but was decreased slowly to 61.3% in 30-day soil, 38.2% in 45-day soil, resumed to 9% similar to the level of control in 75-day soil. In 60-day soil showing 70% degradation rate on total ethoprophos contents of control soil, members of genera Collimonas, Sphingobium, Massilia appeared suddenly in large amounts in its microbial community. These results indicate that these genera including Pseudomonas might majorly be responsible for the real degradation by a natural microbial community in ethoprophos over-contaminated soils.

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