Mercury methylation converts inorganic mercury into the toxic methylmercury, and the consequences of this transformation are worrisome for human health and the environment. This process is performed by anaerobic microorganisms, such as several strains related to Pseudodesulfovibrio and Desulfovibrio genera. In order to provide new insights into the molecular mechanisms of mercury methylation, we performed a comparative genomic analysis on mercury methylators and non-methylators from (Pseudo)Desulfovibrio strains. Our results showed that (Pseudo)Desulfovibrio species are phylogenetically and metabolically distant and consequently, these genera should be divided into various genera. Strains able to perform methylation are affiliated with one branch of the phylogenetic tree, but, except for hgcA and hgcB genes, no other specific genetic markers were found among methylating strains. hgcA and hgcB genes can be found adjacent or separated, but proximity between those genes does not promote higher mercury methylation. In addition, close examination of the non-methylator Pseudodesulfovibrio piezophilus C1TLV30 strain, showed a syntenic structure that suggests a recombination event and may have led to hgcB depletion. The genomic analyses identify also arsR gene coding for a putative regulator upstream hgcA. Both genes are cotranscribed suggesting a role of ArsR in hgcA expression and probably a role in mercury methylation.

中文翻译：

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Desulfovibrio和Pseudodesulfovibrio菌株中汞甲基化的基因组见解。

甲基化汞将无机汞转化为有毒的甲基汞，这种转化的后果对于人类健康和环境而言是令人担忧的。该过程由厌氧微生物，例如与假脱硫弧菌和脱硫弧菌属有关的几种菌株进行。为了提供有关汞甲基化分子机制的新见解，我们对（Pseudo）Desulfovibrio菌株中的汞甲基化剂和非甲基化剂进行了比较基因组分析。我们的结果表明，（假）脱硫弧菌属在系统发育和代谢上均较远，因此，这些属应分为不同的属。能够进行甲基化的菌株与系统发育树的一个分支相关，但是除了hgcA和hgcB基因外，在甲基化菌株中未发现其他特异性遗传标记。hgcA和hgcB基因可以相邻或分开，但这些基因之间的接近性不会促进更高的汞甲基化。此外，仔细检查非甲基化假单胞菌伪狂热C1TLV30菌株，显示出提示重组事件的同系结构，并可能导致hgcB耗竭。基因组分析还确定了编码假定的调节子上游hgcA的arsR基因。这两个基因被共转录，表明ArsR在hgcA表达中的作用，并可能在汞甲基化中起作用。仔细检查非甲基化假单胞菌伪狂犬病C1TLV30菌株，显示出提示重组事件的同系结构，可能导致hgcB耗竭。基因组分析还确定了编码假定的调节子上游hgcA的arsR基因。这两个基因被共转录，表明ArsR在hgcA表达中的作用，并可能在汞甲基化中起作用。仔细检查非甲基化假单胞菌伪狂犬病C1TLV30菌株，显示出提示重组事件的同系结构，可能导致hgcB耗竭。基因组分析还确定了编码假定的调节子上游hgcA的arsR基因。这两个基因被共转录，表明ArsR在hgcA表达中的作用，并可能在汞甲基化中起作用。