Anses, INRAE, Ecole Nationale Vétérinaire d'Alfort, UMR BIPAR, Laboratoire de Santé Animale, 94700, Maisons-Alfort, France.
Department of Zoology, University of Oxford, Oxford, OX1 3SZ, UK.
Sci Rep. 2022 Aug 18;12(1):14045. doi: 10.1038/s41598-022-18269-7.
Protective microbes have a major role in shaping host-pathogen interactions, but their relative importance in the structure of the host microbiota remains unclear. Here, we used a network approach to characterize the impact of a novel, experimentally evolved 'protective microbial symbiont' (Enterococcus faecalis) on the structure and predicted function of the natural microbiota of the model organism Caenorhabditis elegans. We used microbial network analysis to identify keystone taxa and describe the hierarchical placement of protective and non-protective symbionts in the microbiota. We found that early colonization with symbionts produce statistically significant changes in the structure of the community. Notably, only the protective E. faecalis became a keystone taxon in the nematode microbiota. Non-protective lineages of the same bacterial species remained comparatively unimportant to the community. Prediction of functional profiles in bacterial communities using PICRUSt2 showed that the presence of highly protective E. faecalis decreased the abundance of ergothioneine (EGT) biosynthesis pathway involved in the synthesis of the antioxidant molecule EGT, a potential public good. These data show that in addition to direct antagonism with virulent pathogens, keystone protective symbionts are linked to modified bacterial community structure and possible reductions in public goods, potentially driving decreased antioxidant defense. We suggest that this response could suppress infection via wholesale microbial community changes to further benefit the host. These findings extend the concept of protective symbionts beyond bodyguards to ecosystem engineers.
保护微生物在塑造宿主-病原体相互作用方面起着重要作用，但它们在宿主微生物组结构中的相对重要性仍不清楚。在这里，我们使用网络方法来描述一种新型的、经过实验进化的“保护性微生物共生体”（粪肠球菌）对模型生物秀丽隐杆线虫的天然微生物组的结构和预测功能的影响。我们使用微生物网络分析来识别关键分类群，并描述保护性和非保护性共生体在微生物组中的层次位置。我们发现，共生体的早期定植会导致群落结构发生统计学上显著的变化。值得注意的是，只有保护性的粪肠球菌成为线虫微生物组中的关键分类群。同一细菌物种的非保护性谱系在群落中相对不重要。使用 PICRUSt2 预测细菌群落的功能谱表明，高度保护性的粪肠球菌的存在降低了涉及抗氧化分子 EGT 合成的 ergothioneine (EGT) 生物合成途径的丰度，EGT 是一种潜在的公共利益。这些数据表明，除了与毒力病原体的直接拮抗作用外，关键的保护性共生体还与细菌群落结构的改变和可能减少公共利益有关，这可能会降低抗氧化防御。我们认为，这种反应可以通过对微生物群落进行全面改变来抑制感染，从而进一步使宿主受益。这些发现将保护性共生体的概念从保镖扩展到生态系统工程师。
