Krumholz Lee R, Bradstock Peter, Sheik Cody S, Diao Yiwei, Gazioglu Ozcan, Gorby Yuri, McInerney Michael J
Department of Microbiology and Plant Biology, The University of Oklahoma, Norman, Oklahoma, USA Institute for Energy and the Environment, The University of Oklahoma, Norman, Oklahoma, USA
Department of Microbiology and Plant Biology, The University of Oklahoma, Norman, Oklahoma, USA.
Appl Environ Microbiol. 2015 Apr;81(7):2339-48. doi: 10.1128/AEM.03358-14. Epub 2015 Jan 23.
In anaerobic environments, mutually beneficial metabolic interactions between microorganisms (syntrophy) are essential for oxidation of organic matter to carbon dioxide and methane. Syntrophic interactions typically involve a microorganism degrading an organic compound to primary fermentation by-products and sources of electrons (i.e., formate, hydrogen, or nanowires) and a partner producing methane or respiring the electrons via alternative electron accepting processes. Using a transposon gene mutant library of the sulfate-reducing Desulfovibrio alaskensis G20, we screened for mutants incapable of serving as the electron-accepting partner of the butyrate-oxidizing bacterium, Syntrophomonas wolfei. A total of 17 gene mutants of D. alaskensis were identified as incapable of serving as the electron-accepting partner. The genes identified predominantly fell into three categories: membrane surface assembly, flagellum-pilus synthesis, and energy metabolism. Among these genes required to serve as the electron-accepting partner, the glycosyltransferase, pilus assembly protein (tadC), and flagellar biosynthesis protein showed reduced biofilm formation, suggesting that each of these components is involved in cell-to-cell interactions. Energy metabolism genes encoded proteins primarily involved in H2 uptake and electron cycling, including a rhodanese-containing complex that is phylogenetically conserved among sulfate-reducing Deltaproteobacteria. Utilizing an mRNA sequencing approach, analysis of transcript abundance in wild-type axenic and cocultures confirmed that genes identified as important for serving as the electron-accepting partner were more highly expressed under syntrophic conditions. The results imply that sulfate-reducing microorganisms require flagellar and outer membrane components to effectively couple to their syntrophic partners; furthermore, H2 metabolism is essential for syntrophic growth of D. alaskensis G20.
在厌氧环境中，微生物之间互利的代谢相互作用（互营共生）对于将有机物氧化为二氧化碳和甲烷至关重要。互营共生相互作用通常涉及一种微生物将有机化合物降解为初级发酵副产物和电子源（即甲酸盐、氢气或纳米线），以及一个伙伴产生甲烷或通过替代电子接受过程呼吸电子。我们利用硫酸盐还原菌阿拉斯加脱硫弧菌G20的转座子基因突变文库，筛选出不能作为丁酸氧化细菌沃氏互营单胞菌电子接受伙伴的突变体。总共鉴定出17个阿拉斯加脱硫弧菌的基因突变体不能作为电子接受伙伴。鉴定出的基因主要分为三类：膜表面组装、鞭毛菌毛合成和能量代谢。在作为电子接受伙伴所需的这些基因中，糖基转移酶、菌毛组装蛋白（tadC）和鞭毛生物合成蛋白的生物膜形成减少，表明这些成分中的每一个都参与细胞间相互作用。能量代谢基因编码的蛋白质主要参与氢气摄取和电子循环，包括一种含硫代硫酸酶的复合物，该复合物在硫酸盐还原的δ-变形菌中具有系统发育保守性。利用mRNA测序方法，对野生型无菌培养物和共培养物中转录本丰度的分析证实，被鉴定为对作为电子接受伙伴很重要的基因在互营共生条件下表达更高。结果表明，硫酸盐还原微生物需要鞭毛和外膜成分才能有效地与它们的互营共生伙伴耦合；此外，氢气代谢对于阿拉斯加脱硫弧菌G20的互营共生生长至关重要。
