| abstract |
Method of isolating deletion mutants of Vibrio cholerae, wherein the deletion is predetermined by digestion with restriction endonucleases of known specificity. The deletions are inserted into the Vibrio cholerae chromosome by in vivo recombination between a plasmid carrying the desired deletion, with adjacent flanking sequences, and the Vibrio cholerae chromosome. The invention includes the isolation and characterization of a new Vibrio cholerae strain, (ATCC No. 55456), having a deletion in the tox gene, as defined by Acc I, Xba I, Cla I and/or restriction endonuclease sites, and carrying a mercury resistance gene. The invention also includes vaccines for protecting against the symptoms of cholera as well as methods for achieving this protection. |