全基因组重测序研究长期铬胁迫对希瓦氏菌MR-1的影响机制

在实验室纯培养条件下，设计了希瓦氏菌MR-1在恒定浓度Cr（VI）和Cr（Ⅲ）环境中长期胁迫120d实验，探讨了胁迫后的菌株对Cr（VI）的还原能力和生长情况，采用电化学分析仪表征其电化学性质的变化，并且利用全基因组重测序技术分析了不同条件胁迫后不同阶段的菌株基因变异信息.结果表明，Cr（VI）长期胁迫下明显提高了菌株对Cr（VI）的耐受性和还原能力，在38h左右能完全还原初始Cr（VI）浓度55mg/L；在电位-0.2V还原峰附近，细胞色素c与核黄素的结合作用有明显差异；通过重测序结果发现，Cr（VI）长期胁迫下的菌株发生突变的基因点位明显高于Cr（Ⅲ）环境.Cr（Ⅲ）环境胁迫下的非同义突变基因主要集中在葡萄糖转化及合成相关功能的基因、编码呼吸链酶和合成ATP酶的相关基因、编码信号转导和跨膜转运蛋白相关基因，Cr（VI）环境胁迫120d后，主要涉及细胞膜组分基因，转运蛋白、信号转导相关基因，DNA合成、修复相关基因和氧化还原活性相关.

Mechanism of long-term chromium stress on Shewanella oneidensis MR-1using whole genome resequencing technique

The 120-day long-term stress of constant concentration of Cr(VI) and Cr(Ⅲ) on Shewanella oneidensis MR-1 was investigated in the present study. The reduction ability of Cr(VI) and growth were explored after the 120-day cultivation. The electrochemical properties were characterized, and the genetic variation of strains at different stages was analysed using whole genome resequencing technology. The results showed that the long-term stress of Cr(VI) significantly improved the tolerance and reducing ability of Cr(VI). The initial Cr(VI) concentration of 55mg/L was completely reduced within 38h after the 120-day cultivation. There was a significant difference in the binding of cytochrome c to riboflavin near the -0.2V reduction peak between the strains cultured in media with Cr(VI) and Cr(Ⅲ). The mutation gene numbers of strains under long-term Cr(VI) stress were significantly higher than that in Cr(Ⅲ) environment. Non-synonymous mutated genes in strains under Cr(Ⅲ) stress mainly involved in glucose transformation and synthesis, genes encoding respiratory chain enzymes and synthetic ATPase, genes encoding signal transduction and transmembrane transporters. After the 120-day of Cr (VI) stress, mutated genes in strains mainly involved with cell membrane component genes, transporters, signal transduction genes, DNA synthesis repair genes and redox activity.