Data_Sheet_1_Global occurrence of the bacteria with capability for extracellular reduction of iodate.PDF

The γ-proteobacterium Shewanella oneidensis MR-1 reduces iodate to iodide extracellularly. Both dmsEFAB and mtrCAB gene clusters are involved in extracellular reduction of iodate by S. oneidensis MR-1. DmsEFAB reduces iodate to hypoiodous acid and hydrogen peroxide (H2O2). Subsequently, H2O2 is reduced by MtrCAB to facilitate DmsEFAB-mediated extracellular reduction of iodate. To investigate the distribution of bacteria with the capability for extracellular reduction of iodate, bacterial genomes were systematically searched for both dmsEFAB and mtrCAB gene clusters. The dmsEFAB and mtrCAB gene clusters were found in three Ferrimonas and 26 Shewanella species. Coexistence of both dmsEFAB and mtrCAB gene clusters in these bacteria suggests their potentials for extracellular reduction of iodate. Further analyses demonstrated that these bacteria were isolated from a variety of ecosystems, including the lakes, rivers, and subsurface rocks in East and Southeast Asia, North Africa, and North America. Importantly, most of the bacteria with both dmsEFAB and mtrCAB gene clusters were found in different marine environments, which ranged from the Arctic Ocean to Antarctic coastal marine environments as well as from the Atlantic Ocean to the Indian and Pacific Oceans. Widespread distribution of the bacteria with capability for extracellular reduction of iodate around the world suggests their significant importance in global biogeochemical cycling of iodine. The genetic organization of dmsEFAB and mtrCAB gene clusters also varied substantially. The identified mtrCAB gene clusters often contained additional genes for multiheme c-type cytochromes. The numbers of dmsEFAB gene cluster detected in a given bacterial genome ranged from one to six. In latter, duplications of dmsEFAB gene clusters occurred. These results suggest different paths for these bacteria to acquire their capability for extracellular reduction of iodate.

γ-变形菌（γ-proteobacterium）奥奈达希瓦氏菌MR-1（Shewanella oneidensis MR-1）可通过胞外途径将碘酸盐还原为碘化物。dmsEFAB基因簇（dmsEFAB gene cluster）与mtrCAB基因簇（mtrCAB gene cluster）均参与奥奈达希瓦氏菌MR-1对碘酸盐的胞外还原过程。DmsEFAB可将碘酸盐还原为次碘酸与过氧化氢（H₂O₂）；随后，MtrCAB可还原过氧化氢，以辅助DmsEFAB介导的碘酸盐胞外还原反应。为探究具备碘酸盐胞外还原能力的细菌的分布规律，研究人员系统性地在细菌基因组中检索dmsEFAB与mtrCAB基因簇。研究人员在3个费里莫纳斯菌属（Ferrimonas）物种与26个希瓦氏菌属（Shewanella）物种中均发现了上述两种基因簇。这些细菌同时携带dmsEFAB与mtrCAB基因簇，提示其具备碘酸盐胞外还原的潜在能力。进一步分析显示，这些细菌分离自多种生态系统，涵盖东亚、东南亚、北非及北美的湖泊、河流与地下岩石生境。值得关注的是，携带双基因簇的细菌多数分布于不同海洋生境，其分布范围从北冰洋延伸至南极沿海海域，同时覆盖大西洋、印度洋与太平洋海域。具备碘酸盐胞外还原能力的细菌在全球范围内广泛分布，这表明其在全球碘的生物地球化学循环中具有重要作用。dmsEFAB与mtrCAB基因簇的遗传组织结构亦存在显著差异。已鉴定的mtrCAB基因簇通常额外携带多血红素c型细胞色素（multiheme c-type cytochromes）的编码基因。单个细菌基因组中检测到的dmsEFAB基因簇数量介于1至6个不等，其中部分菌株的dmsEFAB基因簇发生了复制。上述结果表明，这些细菌通过不同途径获得了碘酸盐胞外还原的能力。