六价铬[Cr(VI)]是一种常见的环境污染物。然而,对Cr(VI)胁迫下微生物进化的遗传基础以及先前的进化史对Cr(VI)胁迫下后续进化的影响知之甚少。在这项研究中,寻常脱硫弧菌希登伯勒(DvH),一种硫酸盐还原细菌模型,实验进化了600代。通过进化三个基因不同的DvH克隆的复制种群,包括祖先(AN,没有先前的实验进化史),非应激进化的EC3-10和盐应激进化的ES9-11,适应性的贡献,机会,并且能够解剖Cr(VI)胁迫下进化的预先存在的遗传差异。在大多数进化种群中观察到Cr(VI)胁迫下显着减少的滞后期,而Cr(VI)减少率增加主要在EC3-10和ES9-11进化而来的种群中观察到。起始克隆中预先存在的遗传差异对滞后期的变化显示出强烈的影响,增长率,和Cr(VI)还原率。此外,从不同起始克隆进化而来的群体的基因组突变谱有显著差异。共有14个新突变基因在至少两个进化种群中获得突变,表明它们在Cr(VI)适应中的重要性。这些基因之一的框内缺失突变,铬酸盐转运蛋白基因DVU0426表明它在Cr(VI)耐受中起重要作用。总的来说,我们的研究确定了Cr(VI)耐受性的潜在关键功能基因,并证明了在Cr(VI)胁迫条件下预先存在的遗传差异在进化中的重要作用。铬是土壤和地下水中最常见的重金属污染物之一。以前报道了普通脱硫弧菌在重金属生物修复中的潜力,例如Cr(VI)还原;但是,与Cr(VI)抗性有关的关键功能基因的实验证据在很大程度上是未知的。鉴于自然界中微生物种群的遗传差异,关于这种差异如何影响微生物对诸如Cr(VI)胁迫之类的新环境的适应的知识非常有限。利用我们之前的研究,在Cr(VI)胁迫下繁殖了三组具有或不具有先前实验进化史的普通D.vulgarisHildenborough种群600代。进化种群的全种群基因组重测序揭示了Cr(VI)耐受性提高的潜在基因组变化。在表型和遗传水平上都证明了起始克隆中预先存在的遗传差异对Cr(VI)胁迫条件下的进化的强烈影响。
Hexavalent chromium [Cr(VI)] is a common environmental pollutant. However, little is known about the genetic basis of microbial evolution under Cr(VI) stress and the influence of the prior evolution histories on the subsequent evolution under Cr(VI) stress. In this
study, Desulfovibrio vulgaris Hildenborough (DvH), a model sulfate-reducing bacterium, was experimentally evolved for 600 generations. By evolving the replicate populations of three genetically diverse DvH clones, including ancestor (AN, without prior experimental evolution history), non-stress-evolved EC3-10, and salt stress-evolved ES9-11, the contributions of adaptation, chance, and pre-existing genetic divergence to the evolution under Cr(VI) stress were able to be dissected. Significantly decreased lag phases under Cr(VI) stress were observed in most evolved populations, while increased Cr(VI) reduction rates were primarily observed in populations evolved from EC3-10 and ES9-11. The pre-existing genetic divergence in the starting clones showed strong influences on the changes in lag phases, growth rates, and Cr(VI) reduction rates. Additionally, the genomic mutation spectra in populations evolved from different starting clones were significantly different. A total of 14 newly mutated genes obtained mutations in at least two evolved populations, suggesting their importance in Cr(VI) adaptation. An in-frame deletion mutation of one of these genes, the chromate transporter gene DVU0426, demonstrated that it played an important role in Cr(VI) tolerance. Overall, our
study identified potential key functional genes for Cr(VI) tolerance and demonstrated the important role of pre-existing genetic divergence in evolution under Cr(VI) stress conditions. IMPORTANCE Chromium is one of the most common heavy metal pollutants of soil and groundwater. The potential of Desulfovibrio vulgaris Hildenborough in heavy metal bioremediation such as Cr(VI) reduction was reported previously; however, experimental evidence of key functional genes involved in Cr(VI) resistance are largely unknown. Given the genetic divergence of microbial populations in nature, knowledge on how this divergence affects the microbial adaptation to a new environment such as Cr(VI) stress is very limited. Taking advantage of our previous
study, three groups of genetically diverse D. vulgaris Hildenborough populations with or without prior experimental evolution histories were propagated under Cr(VI) stress for 600 generations. Whole-population genome resequencing of the evolved populations revealed the genomic changes underlying the improved Cr(VI) tolerance. The strong influence of the pre-existing genetic divergence in the starting clones on evolution under Cr(VI) stress conditions was demonstrated at both phenotypic and genetic levels.