Butler Jessica E, Young Nelson D, Lovley Derek R
Department of Microbiology, 203 Morrill Science Center IVN, University of Massachusetts, Amherst, MA 01003, USA.
BMC Genomics. 2009 Mar 11;10:103. doi: 10.1186/1471-2164-10-103.
The anaerobic degradation of organic matter in natural environments, and the biotechnical use of anaerobes in energy production and remediation of subsurface environments, both require the cooperative activity of a diversity of microorganisms in different metabolic niches. The Geobacteraceae family contains members with three important anaerobic metabolisms: fermentation, syntrophic degradation of fermentation intermediates, and anaerobic respiration.
In order to learn more about the evolution of anaerobic microbial communities, the genome sequences of six Geobacteraceae species were analyzed. The results indicate that the last common Geobacteraceae ancestor contained sufficient genes for anaerobic respiration, completely oxidizing organic compounds with the reduction of external electron acceptors, features that are still retained in modern Geobacter and Desulfuromonas species. Evolution of specialization for fermentative growth arose twice, via distinct lateral gene transfer events, in Pelobacter carbinolicus and Pelobacter propionicus. Furthermore, P. carbinolicus gained hydrogenase genes and genes for ferredoxin reduction that appear to permit syntrophic growth via hydrogen production. The gain of new physiological capabilities in the Pelobacter species were accompanied by the loss of several key genes necessary for the complete oxidation of organic compounds and the genes for the c-type cytochromes required for extracellular electron transfer.
The results suggest that Pelobacter species evolved parallel strategies to enhance their ability to compete in environments in which electron acceptors for anaerobic respiration were limiting. More generally, these results demonstrate how relatively few gene changes can dramatically transform metabolic capabilities and expand the range of environments in which microorganisms can compete.
自然环境中有机物的厌氧降解以及在能源生产和地下环境修复中厌氧菌的生物技术应用，都需要不同代谢生态位中多种微生物的协同活动。地杆菌科包含具有三种重要厌氧代谢的成员：发酵、发酵中间体的互营降解和厌氧呼吸。
为了更多地了解厌氧微生物群落的进化，分析了六种地杆菌科物种的基因组序列。结果表明，地杆菌科的最后一个共同祖先含有足够的厌氧呼吸基因，能够通过还原外部电子受体完全氧化有机化合物，这些特征在现代地杆菌属和脱硫单胞菌属物种中仍然保留。通过不同的横向基因转移事件，在乙醇氧化栖细菌和丙酸栖细菌中，发酵生长的特化进化出现了两次。此外，乙醇氧化栖细菌获得了氢化酶基因和铁氧化还原蛋白还原基因，这些基因似乎允许通过产氢进行互营生长。在栖细菌属物种中获得新的生理能力的同时，伴随着有机化合物完全氧化所需的几个关键基因以及细胞外电子转移所需的c型细胞色素基因的丢失。
结果表明，栖细菌属物种进化出了平行策略，以增强其在厌氧呼吸电子受体有限的环境中的竞争能力。更普遍地说，这些结果证明了相对较少的基因变化如何能够显著改变代谢能力并扩大微生物能够竞争的环境范围。
