Isolation Of Anaerobic Degrading Bacteria Of Atrazine In Soil And Studies On The Degrading Characteristics

Atrazine,a"selectively inner attract"herbicide,had become the largest production of pesticides varieties and was commonly used all over the world.The overuse of atrazine caused phytotoxicity to the sensitive crops in farmland.It also lead to pollution of farmland soil,surface water and groundwater,which causing the ecological environment destroying and human health threatening.The purpose of this study was to isolate an atrazine-degrading bacteria strain from contaminated soil and to study for the growth and degradation of degrading bacteria based on the current research on atrazine microbial degradation.Then growth conditions for bacteria were optimized and degraded genes were explored.The main research content is as follows:A bacteria strain which took atrazine as the only carbon and nitrogen source,was isolated from long-term atrazine-contaminated soils under anaerobic conditions.The methods of morphological characteristics,16S rDNA identification,and genome scan were used to identify the bacteria.The atrazine-degrading bacteria LG-1 had a homology sequence similarity of more than 99%with Enterobacter Absuriae L1.The growth conditions of the atrazine-degrading bacteria LG-1 were studied.The optimum pH of the bacteria was about 7.0,the optimum growth temperature was30°C,the amount of extra carbon source?sucrose?was 5 g·L^-1,and the substrate?atrazine?concentration is 200 mg·L^-1.The degradation conditions of the degrading bacterium LG-1 were studied.The optimum pH for degradation of atrazine was 7.0 or so,and the optimum temperature was 30°C.It was inoculated at 5%volume for Atrazine concentration of 200 mg·L^-1.The bacteria can achieve a degradation rate of86%within 96 hours.The genomic sequences of LG-1 was assembled.The measured genomic sequence had a length of 4.15 Mb and consisted of 54.47%of G+C%.It contained 111 contigs,the longest of those was 700307 bp,and 153 scaffolds,the longest of those was1,512,473 bp.4501 coding sequences was annotated.The key functional genes that degraded atrazine in LG-1 were cloned and sequenced.The transposon was inserted into the genomic DNA of LG-1 using a parental method to construct a random insertion mutant library.The mutants were inoculated on an inorganic solid medium with atrazine as the only carbon source,so as to make it possible to make the hydrolyzed circle in the solid medium a screening marker,and to suppress the production of a hydrolytic circle in the solid medium.The amplification and sequencing of mutant flanking sequences were on the way.