Enterococcus faecalis Gluconate Phosphotransferase System Accelerates Experimental Colitis and Bacterial Killing by Macrophages.

Enterococcus faecalis strains are resident intestinal bacteria associated with invasive infections, inflammatory bowel diseases, and colon cancer. Although factors promoting E. faecalis colonization of intestines are not fully known, one implicated pathway is a phosphotransferase system (PTS) in E. faecalis strain OG1RF that phosphorylates gluconate and contains the genes OG1RF_12399 to OG1RF_12402 (OG1RF_12399-12402). We hypothesize that this PTS permits growth in gluconate, facilitates E. faecalis intestinal colonization, and exacerbates colitis. We generated E. faecalis strains containing deletions/point mutations in this PTS and measured bacterial growth and PTS gene expression in minimal medium supplemented with selected carbohydrates. We show that E. faecalis upregulates OG1RF_12399 transcription specifically in the presence of gluconate and that E. faecalis strains lacking, or harboring a single point mutation in, OG1RF_12399-12402 are unable to grow in minimal medium containing gluconate. We colonized germfree wild-type and colitis-prone interleukin-10-deficient mice with defined bacterial consortia containing the E. faecalis strains and measured inflammation and bacterial abundance in the colon. We infected macrophage and intestinal epithelial cell lines with the E. faecalis strains and measured intracellular bacterial survival and proinflammatory cytokine secretion. The presence of OG1RF_12399-12402 is not required for E. faecalis colonization of the mouse intestine but is associated with an accelerated onset of experimental colitis in interleukin-10-deficient mice, altered bacterial composition in the colon, enhanced E. faecalis survival within macrophages, and increased proinflammatory cytokine secretion by colon tissue and macrophages. Further studies of bacterial carbohydrate metabolism in general, and E. faecalis PTS-gluconate in particular, during inflammation may identify new mechanisms of disease pathogenesis.