Genetic Dissection of Nutrient Acquisition in Diverse Akkermansia Strains

点击翻译按钮获取中文摘要

The link between the intestinal microbiota and human health is well established, yet many of its inhabitants remain poorly characterized. Akkermansia muciniphila is a beneficial intestinal microbe that is positively correlated with the metabolic and immunologic health of its host. Akkermansia typically represents 1- 4% of the intestinal microbiota, and in some individuals, it can exceed 20%. Despite its prevalence, most Akkermansia research has focused on a single strain, and the factors that influence colonization are unknown.      Akkermansia is the only member of the Phylum Verrucomicrobia known to colonize the mammalian intestine, and it occupies a distinct niche where it forages on host mucins. Work from myself and others indicates that Akkermansia exhibits a striking level of genetic diversity with at least four distinct phylogroups, most of which remain uncharacterized. Notably, many Akkermansia lack pathways for assimilatory sulfate reduction, which renders them dependent on exogenous sulfide to produce sulfur containing molecules such as cysteine. This requirement for reduced sulfur can influence microbe-microbe interactions and has the potential to alter H2S levels at the intestinal epithelium. Because H2S acts as a signalling molecule with potent anti-inflammatory effects, alterations of local H2S concentrations could have broad implications for the host and the ecology of the surrounding microbiota.      The long-term vision for this research program is to use genetic approaches to uncover fundamental aspects of colonization among members of the human intestinal microbiota with strain level resolution. In line with this vision, the short-term objectives outlined in this proposal will reveal basic features of Akkermansia biology and the strain-specific interactions influencing colonization. We will investigate: (1) interactions between Akkermansia pili and host glycoproteins; (2) the genetic mechanisms of carbohydrate utilization among diverse Akkermansia strains; and (3) microbe-microbe interactions between specific Akkermansia strains and H2S producing intestinal microbes.      Our lab is in an excellent position to pursue these aims because of our unique resources. These include a collection of Akkermansia strains, a library of Akkermansia transposon mutants, and knowledge of genetic approaches developed during my postdoctoral work to manipulate Akkermansia, which was previously considered genetically intractable. The proposed research will provide training in microbiology, molecular biology, microscopy, high throughput genetic screens, bioinformatics, and working with animal models.      The proposed work will contribute to understanding the ecology of a potential keystone member of the intestinal microbiota. More broadly, this research has important implications for better understanding basic host-microbe and microbe-microbe interactions in the complex ecosystem of the intestinal microbiome.