The mannose-sensitive hemagglutinin of Vibrio cholerae promotes adherence to zooplankton

The bacterium Vibrio cholerae, the etiological agent of cholera, is often f ound attached to plankton, a property that is thought to contribute to its environmental persistence in aquatic habitats. The C: cholerae O1 EI Tor bi otype and V cholerae O139 strains produce a surface pilus termed the mannos e-sensitive hemagglutinin (MSHA), whereas V. cholerae O1 classical biotype strains do not. Although I I cholerae O1 classical does not elaborate R ISI -LJ, the gene is present and expressed at a level comparable to that of the other strains. Since V. cholerae O1 El Tor and V. cholerae O139 have displ aced I. cholerae O1 classical as the major epidemic strains over the last f ifteen Sears, we investigated the potential role of MSHA in mediating adher ence to plankton, We found that mutation of mshA in V cholerae O1 EI Tor si gnificantly diminished, but did not eliminate, adherence to exoskeletons of the planktonic crustacean Daphnia pulex. The effect of the mutation was mo re pronounced for I: cholerae O139, essentially eliminating adherence. Adhe rence of the V. cholerae O1 classical mskA mutant was unaffected. The resul ts suggest that MSW is a factor contributing to the ability of T cholerae t o adhere to plankton, The results also showed that both biotypes of lr chol erae O1 utilize factors in addition to MSHA for zooplankton adherence. The expression of MSHA and these additional, yet to be defined, adherence facto rs differ in a serogroup- and biotype-specific manner.