Pivotal roles for pH, lactate and lactate-utilizing bacteria in the stability of a human colonic microbial ecosystem

Lactate is a fermentation byproduct produced by a number of colonic microbes and accumulation of this compound in the human colon has been linked to disorders such as ulcerative colitis. In health, lactate typically does not accumulate as it is consumed by specific groups of lactate-utilising anaerobes and converted into health promoting short chain fatty acids such as butyrate. In order to identify a broad range of lactate utilising bacteria, and to understand their ability to respond to varying pH and lactate supply conditions, we applied 16S rRNA gene sequencing to continuous culture fermentor vessels inoculated with human faecal microbiota.