阿特拉津降解菌Arthrobacter sp. AG1降解基因研究

Study on the Atrazine-degrading Genes in Arthrobacter sp. AG1

摘要:

菌株Arthrobacter sp. AG1能以4000 mg/L的阿特拉津（AT）为唯一碳源、氮源和能源生长。通过设计特异引物从AG1中扩增出阿特拉津氯水解酶基因trzN的全序列，该基因与已报道的trzN基因序列相似性为99%。AG1菌株中含有两个大于100kb的质粒，Southern杂交结果显示trzN和atzB基因均位于其中较大的一个质粒pAG1上。将AG1菌株在LB液体培养基中转接三代后，发现34%的细菌细胞丢失了降解活性，但却未发现丢失质粒，PCR扩增结果表明突变子丢失了trzN基因，但atzB和atzC基因未丢失，说明降解活性的缺失是trzN基因片段从质粒上丢失的结果，表明trzN基因在环境中存在水平转移现象，暗示菌株AG1中的阿特拉津降解基因是基因的水平转移重组的结果。

Abstract:

Atrazine could be used as the sole carbon，nitrogen and energy sources for growth by strain Arthrobacter sp. AG1，and the atrazine-degrading genes of AG1 were found to be the combination of trzN，atzB and atzC. The atrazine chloride hydrolysase gene trzN was cloned by PCR amplification，whose sequence shared 99% identity with that of Norcardioides sp. C190. Two large plasmids were found in AG1，and trzN and atzB were confirmed to be localized on the larger plasmid pAG1 by the method of southern hybridization. Subculture of AG1 in liquid LB for three generations，34% of the subsequent cells were found to lose degrading activity，however，neither plasmid was lost. PCR amplification results showed that the mutants had only lost the trzN gene instead of atzB and atzC. It was deduced that mutation might be due to the trzN gene deletion from the plasmid. This study provided new evidence that atrazine metabolic genotypes were resulted from horizontal gene transfer between different bacteria under environmental selective pressure.