Department of Microbiology and Immunology, Thermal Biology Institute, Montana State University, Bozeman, MT 59717-3520, USA.
Department of Biochemistry and Microbiology, Graduate Program in Ecology and Evolution, Rutgers University, New Brunswick, NJ 08901-8525, USA.
Sci Total Environ. 2016 Nov 1;569-570:321-331. doi: 10.1016/j.scitotenv.2016.06.080. Epub 2016 Jun 24.
Because geothermal environments contain mercury (Hg) from natural sources, microorganisms that evolved in these systems have likely adapted to this element. Knowledge of the interactions between microorganisms and Hg in geothermal systems may assist in understanding the long-term evolution of microbial adaptation to Hg with relevance to other environments where Hg is introduced from anthropogenic sources. A number of microbiological studies with supporting geochemistry have been conducted in geothermal systems across western North America. Approximately 1 in 5 study sites include measurements of Hg. Of all prokaryotic taxa reported across sites with microbiological and accompanying physicochemical data, 42% have been detected at sites in which Hg was measured. Genes specifying Hg reduction and detoxification by microorganisms were detected in a number of hot springs across the region. Archaeal-like sequences, representing two crenarchaeal orders and one order each of the Euryarchaeota and Thaumarchaeota, dominated in metagenomes' MerA (the mercuric reductase protein) inventories, while bacterial homologs were mostly found in one deeply sequenced metagenome. MerA homologs were more frequently found in metagenomes of microbial communities in acidic springs than in circumneutral or high pH geothermal systems, possibly reflecting higher bioavailability of Hg under acidic conditions. MerA homologs were found in hot springs prokaryotic isolates affiliated with Bacteria and Archaea taxa. Acidic sites with high Hg concentrations contain more of Archaea than Bacteria taxa, while the reverse appears to be the case in circumneutral and high pH sites with high Hg concentrations. However, MerA was detected in only a small fraction of the Archaea and Bacteria taxa inhabiting sites containing Hg. Nevertheless, the presence of MerA homologs and their distribution patterns in systems, in which Hg has yet to be measured, demonstrates the potential for detoxification by Hg reduction in these geothermal systems, particularly the low pH springs that are dominated by Archaea.
由于地热环境中含有来自自然源的汞（Hg），因此在这些系统中进化的微生物可能已经适应了这种元素。了解微生物与地热系统中 Hg 之间的相互作用，可能有助于理解微生物对 Hg 的长期适应进化，这与其他从人为源引入 Hg 的环境有关。在北美西部的多个地热系统中已经进行了许多有微生物学支持的地球化学研究。大约有 1/5 的研究地点包括 Hg 测量值。在有微生物学和伴随的物理化学数据的所有报告的原核生物分类群中，有 42%是在测量 Hg 的地点检测到的。在该地区的许多温泉中都检测到了指定微生物 Hg 还原和解毒的基因。古菌样序列代表两个泉古菌门和一个广古菌门和泉古菌门的订单，在宏基因组的 MerA（汞还原酶蛋白）目录中占主导地位，而细菌同源物主要存在于一个深度测序的宏基因组中。MerA 同源物在酸性泉中的微生物群落的宏基因组中比在近中性或高 pH 地热系统中更频繁地发现，这可能反映了在酸性条件下 Hg 的生物利用度更高。MerA 同源物在与细菌和古菌分类群相关的温泉原核分离物中被发现。高 Hg 浓度的酸性地点含有比细菌分类群更多的古菌，而在近中性和高 pH 高 Hg 浓度的地点则相反。然而，MerA 仅在含有 Hg 的少数几个栖息的古菌和细菌分类群中被检测到。尽管如此，在尚未测量 Hg 的系统中，MerA 同源物的存在及其分布模式表明了这些地热系统中通过 Hg 还原解毒的潜力，特别是由古菌主导的低 pH 温泉。
