重金属污染环境中的节杆菌群体遗传结构分化

Genetic differentiation of Arthrobacter population from heavy metal-contamin-(ated) environments

从堆积时间分别有10、20a和80a以上的3个矿渣堆5~10cm层面、25~30cm层面采集了6个样品,经测试分析发现它们有极高的Pb,Zn和Cd等重金属含量。在这些样品中分离纯化出48株细菌,经过分析它们的部分16S rRNA基因序列(分析片段长度在474bp^708bp之间变化),发现这些菌株属于节杆菌属的成员,同A rthrobacter key seri和A.ureaf aciens两个种的系统发育地位最为接近,大约600bp碱基片段的序列同源性在99.1%~100%。接下来利用RAPD(R andom ly Am p lifiedPo lym orph ic DNA)技术探讨了该种群在遗传结构上的分化。结果表明来自矿渣A(堆积时间为10a)和矿渣堆C(堆积时间大于80a)的亚群之间遗传分化最大。此外,不论是来自同一个矿渣堆5~10cm层面和25~30cm层面之间的亚群还是来自不同矿渣堆相同深度的亚群,它们之间的遗传距离都随矿渣堆积时间延长而增加。有趣的是各亚群的N e i基因多样性减少同矿渣可溶性Pb含量呈现明显负相关,表明可溶性Pb可能是导致该节杆菌类群遗传多样性减少的主导环境因子。

Six samples contained extremely high concentration of Pb, Zn and Cd were obtained from the layers of 5-10cm and 25-30cm of three tailing piles, with age of about 10, 20 and more than 80 years, respectively. Then forty-eight bacterial strains were obtained from these samples, and subsequently their phylogenetic positions were determined by analysis of the partial sequence of 16S rRNA gene （fragment length ranged from 474 to 708bp）. These isolates were members of Arthrobacter genus, phylogenetically close to A. keyseri and A. ureafaciens, with sequence similarity ranged from 99.1 to 100%. Furthermore, genetic variation between subpopulations from different samples was revealed by analysis of their RAPD profiles. Nei genetic distance showed that the greatest differentiation occurred between subpopulation A and C. Notably, either genetic distance between subpopulations from the layer of 5-10cm and 25-30cm of each tailing pile or between same layers of different tailing pile was increased with the history of tailings. Moreover, correlation analysis showed that soluble Pb was significantly negative relationship with Nei＇ gene diversity of subpopulation. It was assumed that soluble Pb may be responsible for the reduced genetic diversity of Arthrobacter population. Our data provided evidence that genetic differentiation of microbial populations was consistent with the changes of environmental factors, particularly heavy metals.