Microbial Ecology Group, Rowett Institute of Nutrition and Health, Greenburn Road, Bucksburn, Aberdeen, UK.
ISME J. 2012 Aug;6(8):1535-43. doi: 10.1038/ismej.2012.4. Epub 2012 Feb 16.
The release of energy from particulate substrates such as dietary fiber and resistant starch (RS) in the human colon may depend on the presence of specialist primary degraders (or 'keystone species') within the microbial community. We have explored the roles of four dominant amylolytic bacteria found in the human colon in the degradation and utilization of resistant starches. Eubacterium rectale and Bacteroides thetaiotaomicron showed limited ability to utilize RS2- and RS3-resistant starches by comparison with Bifidobacterium adolescentis and Ruminococcus bromii. In co-culture, however, R. bromii proved unique in stimulating RS2 and RS3 utilization by the other three bacterial species, even in a medium that does not permit growth of R. bromii itself. Having previously demonstrated low RS3 fermentation in vivo in two individuals with undetectable populations of R. bromii-related bacteria, we show here that supplementation of mixed fecal bacteria from one of these volunteers with R. bromii, but not with the other three species, greatly enhanced the extent of RS3 fermentation in vitro. This argues strongly that R. bromii has a pivotal role in fermentation of RS3 in the human large intestine, and that variation in the occurrence of this species and its close relatives may be a primary cause of variable energy recovery from this important component of the diet. This work also indicates that R. bromii possesses an exceptional ability to colonize and degrade starch particles when compared with previously studied amylolytic bacteria from the human colon.
能量从膳食纤维和抗性淀粉（RS）等颗粒状基质中的释放可能取决于微生物群落中是否存在专门的初级降解剂（或“基石物种”）。我们已经探索了在人类结肠中发现的四种主要淀粉分解细菌在降解和利用抗性淀粉方面的作用。与双歧杆菌和瘤胃球菌相比，真杆菌和拟杆菌对 RS2-和 RS3-抗性淀粉的利用能力有限。然而，在共培养中，瘤胃球菌被证明具有独特的能力，可以刺激其他三种细菌利用 RS2 和 RS3，即使在不允许瘤胃球菌自身生长的培养基中也是如此。先前在两个 R. bromii 相关细菌检测不到的个体中体内 RS3 发酵水平较低，我们在这里表明，从其中一名志愿者的混合粪便细菌中补充瘤胃球菌，而不是其他三种细菌，大大增强了 RS3 在体外发酵的程度。这有力地表明，瘤胃球菌在人类大肠中 RS3 的发酵中起着关键作用，并且该物种及其密切相关物种的发生变化可能是从饮食中这一重要成分中获得可变能量回收的主要原因。这项工作还表明，与之前研究过的来自人类结肠的淀粉分解细菌相比，瘤胃球菌具有在肠道中定植和降解淀粉颗粒的特殊能力。
