title: Regulation of toxin biosynthesis by plasmids in Vibrio cholerae.
abstract: Vibrio cholerae strain 569B Inaba harbouring P plasmid produced less toxin than the parent strain. To examine the effect of plasmid loss on toxin production, temperature-sensitive (ts) mutants of P, unable to replicate at 42 degrees C, were isolated. One ts plasmid was unstable at 42 degrees C and its loss yielded a cured strain that resumed a normal level of toxin biosynthesis characteristic of the plasmid-free parent strain. Toxin production was again suppressed in the cured strain after reacquisition of P plasmid. This suggested a role for plasmid-borne genes in the regulation of toxin biosynthesis. A mutant of strain 569B Inaba that produced mutant toxin was isolated by transfer of P and V plasmids. The mutant toxin was similar to choleragenoid because it did not give rise to symptoms of cholera but induced antitoxin immunity in rabbits.
mesh_terms: D000818:Animals; D000992:Antitoxins / Q000032:analysis; D002772:Cholera Toxin / Q000096:biosynthesis*; D005779:Immunodiffusion; D009154:Mutation; D010957:Plasmids; D011817:Rabbits; D014734:Vibrio cholerae / Q000378:metabolism*
chemical_list: D000992:Antitoxins; D002772:Cholera Toxin