Department of Microbial Pathogenesis and Microbial Diversity Institute, Yale University, New Haven, CT 06536, USA.
Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA 94720, USA.
Cell Host Microbe. 2014 Jan 15;15(1):47-57. doi: 10.1016/j.chom.2013.12.007.
Genomic and metagenomic sequencing efforts, including human microbiome projects, reveal that microbes often encode multiple systems that appear to accomplish the same task. Whether these predictions reflect actual functional redundancies is unclear. We report that the prominent human gut symbiont Bacteroides thetaiotaomicron employs three functional, homologous vitamin B₁₂ transporters that in at least two cases confer a competitive advantage in the presence of distinct B₁₂ analogs (corrinoids). In the mammalian gut, microbial fitness can be determined by the presence or absence of a single transporter. The total number of distinct corrinoid transporter families in the human gut microbiome likely exceeds those observed in B. thetaiotaomicron by an order of magnitude. These results demonstrate that human gut microbes use elaborate mechanisms to capture and differentiate corrinoids in vivo and that apparent redundancies observed in these genomes can instead reflect hidden specificities that determine whether a microbe will colonize its host.
基因组和宏基因组测序工作，包括人类微生物组计划，揭示了微生物通常编码多个似乎执行相同任务的系统。这些预测是否反映了实际的功能冗余尚不清楚。我们报告称，人类肠道共生菌拟杆菌属（Bacteroides thetaiotaomicron）利用三种功能上同源的维生素 B₁₂转运蛋白，在至少两种情况下，当存在不同的 B₁₂类似物（类钴胺素）时，赋予了竞争优势。在哺乳动物肠道中，微生物的适应性可以由单一转运蛋白的存在或不存在来决定。人类肠道微生物组中不同的类钴胺素转运蛋白家族的总数可能超过了在拟杆菌属中观察到的数量级。这些结果表明，人类肠道微生物在体内使用精细的机制来捕获和区分类钴胺素，而这些基因组中观察到的明显冗余实际上可能反映了决定微生物是否会定植其宿主的隐藏特异性。
