| Glycogen is a highly branched polysaccharide composed of glucose molecules that is used by many organisms as a source of readily available glucose. Many bacteria, including enterics, have been shown to accumulate glycogen. Although the regulation of glycogen metabolism in bacteria has been extensively studied, the role of glycogen metabolism in bacterial survival and pathogenesis is poorly understood. We have found that the Gram-negative facultative pathogen Vibrio cholerae accumulates glycogen during growth on carbon sources encountered throughout its life-cycle. This includes during growth on chitin, the major carbon source in aquatic environments, and during growth on maltose, a major carbon source in the human small intestine. Glycogen granules were found in rice-water stool V. cholerae, suggesting glycogen is stored by V. cholerae during human infection. Glycogen metabolism prolongs survival of V. cholerae in known nutrient poor niches and provides protection against stresses encountered in the environment. In addition, glycogen contributes to the virulence of V. cholerae in a model of transmission. We have defined some of the genetic requirements necessary for glycogen metabolism in V. cholerae. V. cholerae is unique in that it contains two paralogs of a gene necessary for glycogen metabolism, and these are differentially regulated during growth on different sugars encountered during its life-cycle. Our data indicate that glycogen storage is an important element in the transition of V. cholerae between the human host and the aquatic environment. |
