Carbohydrate complexity and maintenance of human gut microbiome diversity

Here we describe community structure of human fecal microbiota under high dilution pressure due to sequential batch cultivation. Fecal microbiota from a single donor were grown in a mineral medium containing either 1) inulin, 2) sorghum arabinoxylan, or 3) monosaccharides mimicking the composition of each to determine whether structuring of carbohydrates maintains diversity. A second experiment is similar in approach, except that the polymers were cultivated with and without exogenous nutrients to determine whether carbohydrate structure or other metabolic interactions were more influential in governing community structure. We evaluated community structure by sequencing the V4-V5 region of the 16S gene, using primers 515FB and 926R. We observed that 1) maintained diversity was related to carbohydrate complexity and 2) communities fermenting more complex carbohydrates were less affected in composition or function by addition of exogenous nutrients.