Isolation and characterization of bacteriophage-resistant mutants of Vibrio cholerae O139

Vibrio cholerae O139 strains produce a capsule which is associated with com plement resistance and is used as a receptor by bacteriophage JA1. Spontane ous JA1-resistant mutants were found to have several phenotypes, with loss of capsule and/or O-antigen from the cell surface. Determination of the res idual complement resistance and infant mouse colonization potential of each mutant suggested that production of O-antigen is of much greater significa nce than the presence of capsular material for both of these properties. Tw o different in vitro assays of complement resistance were compared and the results of one shown to closely reflect the comparative recoveries of bacte ria from the colonization experiments. Preliminary complementation studies implicated two rfb region genes, wzz and wbfP, as being essential for the b iosynthesis of capsule but not O-antigen. (C) 2001 Academic Press.