Growth in a Biofilm Induces a Hyperinfectious Phenotype inVibrio cholerae

Abstract

Biofilm formation plays a multifaceted role in the life cycles of a wide variety of microorganisms. In the case of pathogenicVibrio cholerae, biofilm formation in its native aquatic habitats is thought to aid in persistence during interepidemic seasons and to enhance infectivity upon oral ingestion. The structure ofV. choleraebiofilms has been hypothesized to protect the bacteria during passage through the stomach. Here, we directly test the role of biofilm architecture in the infectivity ofV. choleraeby comparing the abilities of intact biofilms, dispersed biofilms, and planktonic cells to colonize the mouse small intestine. Not only wereV. choleraebiofilms better able to colonize than planktonic cells, but the structure of the biofilm was also found to be dispensable: intact and dispersed biofilms colonized equally, and both vastly out-colonized planktonic cells. The infectious dose for biofilm-derivedV. choleraewas orders of magnitude lower than that of planktonic cells. This biofilm-induced hyperinfectivity may be due in part to a higher growth rate of biofilm-derived cells during infection. These results suggest that the infectious dose of naturally occurring biofilms ofV. choleraemay be much lower than previously estimated using cells grown planktonicallyin vitro. Furthermore, this work implies the existence of factors specifically induced during growth in a biofilm that augment infection byV. cholerae.