PLoS Biol：通过选择性作用进化出肠道有益微生物

近日，刊登在国际杂志PLOS Biology上的一篇研究报告中，来自牛津大学的研究者揭示了，动物，包括人类，都可以积极地选择肠道微生物来作为机体的“伙伴”，并且用机体分泌的营养物来供给肠道微生物。

研究者开发了一种进化型的计算机模型，用以指示动物肠道微生物和肠道上皮细胞之间的相互作用，这种模型可以揭示缓慢生长的有益细菌快速缺失的过程以及其需要通过宿主分泌的营养物所维持生命，不然特异的营养物质可以更好地维持肠道有益细菌的生存。

研究者Kevin说，我们机体中的细胞数量比机体中微生物的数量多很多，我们都知道许多肠道微生物对机体有益，可以保护我们避免致病菌的感染以及帮助消化，但是这种肠道微生物和机体之间的有益关系是如何进行进化的却不得而知。

这项研究揭示了机体中促进生长的营养物质对于控制机体有益微生物的作用，而且这种对微生物的控制作用比我们想象中简单的多。研究者表示，机体可以分泌很多小分子的营养物质，这对于某些肠道微生物来说是一种偏爱作用，使得这些微生物得到足够营养，给机体带来有益的作用。

研究小组的研究揭示了，被宿主上皮细胞选择的细胞是最不可能被丢失的，相反其坚持时间很久，这样就会引发选择性的放大效应，这就是为何机体中相对较小的变化会引发机体大的反应。

编译自：Beneficial Microbes Are 'Selected and Nurtured' in the Human Gut

doi:10.1371/journal.pbio.1001424
PMC:
PMID:

The Evolution of Mutualism in Gut Microbiota Via Host Epithelial Selection

Jonas Schluter1,2*, Kevin R. Foster1,2*

The human gut harbours a large and genetically diverse population of symbiotic microbes that both feed and protect the host. Evolutionary theory, however, predicts that such genetic diversity can destabilise mutualistic partnerships. How then can the mutualism of the human microbiota be explained? Here we develop an individual-based model of host-associated microbial communities. We first demonstrate the fundamental problem faced by a host: The presence of a genetically diverse microbiota leads to the dominance of the fastest growing microbes instead of the microbes that are most beneficial to the host. We next investigate the potential for host secretions to influence the microbiota. This reveals that the epithelium–microbiota interface acts as a selectivity amplifier: Modest amounts of moderately selective epithelial secretions cause a complete shift in the strains growing at the epithelial surface. This occurs because of the physical structure of the epithelium–microbiota interface: Epithelial secretions have effects that permeate upwards through the whole microbial community, while lumen compounds preferentially affect cells that are soon to slough off. Finally, our model predicts that while antimicrobial secretion can promote host epithelial selection, epithelial nutrient secretion will often be key to host selection. Our findings are consistent with a growing number of empirical papers that indicate an influence of host factors upon microbiota, including growth-promoting glycoconjugates. We argue that host selection is likely to be a key mechanism in the stabilisation of the mutualism between a host and its microbiota.

(责任编辑：shentuo)