Dick Gregory J, Podell Sheila, Johnson Hope A, Rivera-Espinoza Yadira, Bernier-Latmani Rizlan, McCarthy James K, Torpey Justin W, Clement Brian G, Gaasterland Terry, Tebo Bradley M
Department of Environmental and Biomolecular Systems, OGI School of Science & Engineering, Oregon Health & Sciences University, 20000 NW Walker Rd., Beaverton, OR 97006, USA.
Appl Environ Microbiol. 2008 May;74(9):2646-58. doi: 10.1128/AEM.01656-07. Epub 2008 Mar 14.
Microbial Mn(II) oxidation has important biogeochemical consequences in marine, freshwater, and terrestrial environments, but many aspects of the physiology and biochemistry of this process remain obscure. Here, we report genomic insights into Mn(II) oxidation by the marine alphaproteobacterium Aurantimonas sp. strain SI85-9A1, isolated from the oxic/anoxic interface of a stratified fjord. The SI85-9A1 genome harbors the genetic potential for metabolic versatility, with genes for organoheterotrophy, methylotrophy, oxidation of sulfur and carbon monoxide, the ability to grow over a wide range of O(2) concentrations (including microaerobic conditions), and the complete Calvin cycle for carbon fixation. Although no growth could be detected under autotrophic conditions with Mn(II) as the sole electron donor, cultures of SI85-9A1 grown on glycerol are dramatically stimulated by addition of Mn(II), suggesting an energetic benefit from Mn(II) oxidation. A putative Mn(II) oxidase is encoded by duplicated multicopper oxidase genes that have a complex evolutionary history including multiple gene duplication, loss, and ancient horizontal transfer events. The Mn(II) oxidase was most abundant in the extracellular fraction, where it cooccurs with a putative hemolysin-type Ca(2+)-binding peroxidase. Regulatory elements governing the cellular response to Fe and Mn concentration were identified, and 39 targets of these regulators were detected. The putative Mn(II) oxidase genes were not among the predicted targets, indicating that regulation of Mn(II) oxidation is controlled by other factors yet to be identified. Overall, our results provide novel insights into the physiology and biochemistry of Mn(II) oxidation and reveal a genome specialized for life at the oxic/anoxic interface.
微生物锰（II）氧化在海洋、淡水和陆地环境中具有重要的生物地球化学意义，但该过程的生理学和生物化学的许多方面仍不清楚。在此，我们报告了对从分层峡湾的有氧/缺氧界面分离出的海洋α-变形菌橙色单胞菌属菌株SI85-9A1进行锰（II）氧化的基因组研究。SI85-9A1基因组具有代谢多样性的遗传潜力，拥有有机异养、甲基营养、硫和一氧化碳氧化、在广泛的氧气浓度范围内（包括微需氧条件）生长的能力以及完整的卡尔文碳固定循环的基因。尽管在以锰（II）作为唯一电子供体的自养条件下未检测到生长，但在甘油上生长的SI85-9A1培养物在添加锰（II）后受到显著刺激，这表明锰（II）氧化带来了能量益处。一个假定的锰（II）氧化酶由重复的多铜氧化酶基因编码，这些基因具有复杂的进化历史，包括多个基因复制、丢失和古老的水平转移事件。锰（II）氧化酶在细胞外部分最为丰富，在那里它与一种假定的溶血素型钙（2+）结合过氧化物酶共同存在。确定了控制细胞对铁和锰浓度反应的调控元件，并检测到这些调控因子的39个靶标。假定的锰（II）氧化酶基因不在预测的靶标之中，这表明锰（II）氧化的调控由其他尚未确定的因素控制。总体而言，我们的结果为锰（II）氧化的生理学和生物化学提供了新的见解，并揭示了一个专门适应有氧/缺氧界面生活的基因组。
