Inskeep William P, Macur Richard E, Hamamura Natsuko, Warelow Thomas P, Ward Seamus A, Santini Joanne M
Thermal Biology Institute, Montana State University, Bozeman, MT 59717 USA.
Environ Microbiol. 2007 Apr;9(4):934-43. doi: 10.1111/j.1462-2920.2006.01215.x.
The arsenic (As) drinking water crisis in south and south-east Asia has stimulated intense study of the microbial processes controlling the redox cycling of As in soil-water systems. Microbial oxidation of arsenite is a critical link in the global As cycle, and phylogenetically diverse arsenite-oxidizing microorganisms have been isolated from various aquatic and soil environments. However, despite progress characterizing the metabolism of As in various pure cultures, no functional gene approaches have been developed to determine the importance and distribution of arsenite-oxidizing genes in soil-water-sediment systems. Here we report for the first time the successful amplification of arsenite oxidase-like genes (aroA/asoA/aoxB) from a variety of soil-sediment and geothermal environments where arsenite is known to be oxidized. Prior to the current work, only 16 aroA/asoA/aoxB-like gene sequences were available in GenBank, most of these being putative assignments from homology searches of whole genomes. Although aroA/asoA/aoxB gene sequences are not highly conserved across disparate phyla, degenerate primers were used successfully to characterize over 160 diverse aroA-like sequences from 10 geographically isolated, arsenic-contaminated sites and from 13 arsenite-oxidizing organisms. The primer sets were also useful for confirming the expression of aroA-like genes in an arsenite-oxidizing organism and in geothermal environments where arsenite is oxidized to arsenate. The phylogenetic and ecological diversity of aroA-like sequences obtained from this study suggests that genes for aerobic arsenite oxidation are widely distributed in the bacterial domain, are widespread in soil-water systems containing As, and play a critical role in the biogeochemical cycling of As.
南亚和东南亚的砷（As）饮用水危机激发了对控制土壤 - 水系统中砷氧化还原循环的微生物过程的深入研究。亚砷酸盐的微生物氧化是全球砷循环中的关键环节，并且已经从各种水生和土壤环境中分离出系统发育多样的亚砷酸盐氧化微生物。然而，尽管在表征各种纯培养物中砷的代谢方面取得了进展，但尚未开发出功能基因方法来确定亚砷酸盐氧化基因在土壤 - 水 - 沉积物系统中的重要性和分布。在此，我们首次报告成功从各种已知亚砷酸盐被氧化的土壤 - 沉积物和地热环境中扩增出亚砷酸盐氧化酶样基因（aroA/asoA/aoxB）。在当前工作之前，GenBank中仅有16个aroA/asoA/aoxB样基因序列，其中大多数是通过全基因组同源性搜索得到的推测性序列。尽管aroA/asoA/aoxB基因序列在不同门之间的保守性不高，但简并引物已成功用于表征来自10个地理上隔离的砷污染位点和13种亚砷酸盐氧化生物的160多个不同的aroA样序列。这些引物组还可用于确认aroA样基因在亚砷酸盐氧化生物和亚砷酸盐被氧化为砷酸盐的地热环境中的表达。从本研究中获得的aroA样序列的系统发育和生态多样性表明，好氧亚砷酸盐氧化基因在细菌域中广泛分布，在含砷的土壤 - 水系统中普遍存在，并在砷的生物地球化学循环中起关键作用。
