Laboratory of Microbial Ecology and Technology, Ghent University, Ghent, Belgium.
FEMS Microbiol Rev. 2011 Jul;35(4):681-704. doi: 10.1111/j.1574-6976.2011.00270.x. Epub 2011 Mar 18.
Along the human gastrointestinal tract, microorganisms are confronted with multiple barriers. Besides selective physical conditions, the epithelium is regularly replaced and covered with a protective mucus layer trapping immune molecules. Recent insights into host defense strategies show that the host selects the intestinal microbiota, particularly the mucosa-associated microbial community. In this context, humans coevolved with thousands of intestinal microbial species that have adapted to provide host benefits, while avoiding pathogenic behavior that might destabilize their host interaction. While mucosal microorganisms would be crucial for immunological priming, luminal microorganisms would be important for nutrient digestion. Further, we propose that the intestinal microorganisms also coevolved with each other, leading to coherently organized, resilient microbial associations. During disturbances, functionally redundant members become more abundant and are crucial for preserving community functionality. The outside of the mucus layer, where host defense molecules are more diluted, could serve as an environment where microorganisms are protected from disturbances in the lumen and from where they can recolonize the lumen after perturbations. This might explain the remarkable temporal stability of microbial communities. Finally, commensals that become renegade or a decreased exposure to essential coevolved microorganisms may cause particular health problems such as inflammatory bowel diseases, obesity or allergies.
在人类的胃肠道中，微生物面临着多种障碍。除了有选择性的物理条件外，上皮细胞会定期更换，并覆盖有保护性的黏液层，从而捕获免疫分子。最近对宿主防御策略的深入了解表明，宿主选择肠道微生物群，特别是黏膜相关的微生物群落。在这种情况下，人类与数千种肠道微生物物种共同进化，这些微生物已经适应了为宿主提供益处，同时避免可能破坏其与宿主相互作用的致病行为。虽然黏膜微生物对于免疫启动至关重要，但腔微生物对于营养消化也很重要。此外，我们提出肠道微生物也相互进化，形成了具有协同作用的、有弹性的微生物关联。在受到干扰时，功能冗余的成员会变得更加丰富，对于维持群落功能至关重要。黏液层的外部，宿主防御分子的浓度较低，可能成为微生物免受腔干扰和在受到干扰后重新定植腔的保护环境。这可能解释了微生物群落的显著时间稳定性。最后，叛变的共生菌或减少与必要的共同进化微生物的接触，可能会导致特定的健康问题，如炎症性肠病、肥胖或过敏。
