Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA.
Exobiology Branch, National Aeronautics and Space Administration Ames Research Center, Moffett Field, California 94035, USA.
Nature. 2015 Oct 22;526(7574):531-5. doi: 10.1038/nature15512. Epub 2015 Sep 16.
Multicellular assemblages of microorganisms are ubiquitous in nature, and the proximity afforded by aggregation is thought to permit intercellular metabolic coupling that can accommodate otherwise unfavourable reactions. Consortia of methane-oxidizing archaea and sulphate-reducing bacteria are a well-known environmental example of microbial co-aggregation; however, the coupling mechanisms between these paired organisms is not well understood, despite the attention given them because of the global significance of anaerobic methane oxidation. Here we examined the influence of interspecies spatial positioning as it relates to biosynthetic activity within structurally diverse uncultured methane-oxidizing consortia by measuring stable isotope incorporation for individual archaeal and bacterial cells to constrain their potential metabolic interactions. In contrast to conventional models of syntrophy based on the passage of molecular intermediates, cellular activities were found to be independent of both species intermixing and distance between syntrophic partners within consortia. A generalized model of electric conductivity between co-associated archaea and bacteria best fit the empirical data. Combined with the detection of large multi-haem cytochromes in the genomes of methanotrophic archaea and the demonstration of redox-dependent staining of the matrix between cells in consortia, these results provide evidence for syntrophic coupling through direct electron transfer.
微生物的多细胞聚集体在自然界中无处不在，聚集提供的接近度被认为允许细胞间的代谢偶联，从而适应否则不利的反应。甲烷氧化古菌和硫酸盐还原菌的共生体是微生物共聚的一个众所周知的环境例子；然而，尽管由于厌氧甲烷氧化的全球重要性而受到关注，但这些成对生物之间的偶联机制仍未得到很好的理解。在这里，我们通过测量结构多样的未培养甲烷氧化共生体中单个古菌和细菌细胞的稳定同位素掺入来检查种间空间定位对生物合成活性的影响，以限制它们潜在的代谢相互作用。与基于分子中间产物传递的传统共营养模型相反，细胞活性与共生体中协同伙伴之间的物种混合和距离无关。电导率在共同相关的古菌和细菌之间的广义模型最符合经验数据。结合甲烷营养古菌基因组中大量多血红细胞色素的检测以及在共生体中细胞之间基质的氧化还原依赖性染色的证明，这些结果为通过直接电子转移进行共营养偶联提供了证据。
