Regulation of Toxin Biosynthesis by Plasmids in Vibrio cholerae

Abstract

2653Vibrio 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 "C, were isolated. One ts plasmid was unstable at 42 "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.

Role of the P plasmid in attenuation of Vibrio cholerae O1

“…Our data show that P, in the presence or absence of V, is dramatically attenuating for this strain; V alone has no effect. Investigation of the mechanism by which P might exert its effect did not support previous reports (18,34) that this plasmid may inhibit the biosynthesis of CT. Whether compared in a rabbit ileal loop system or by a GM1 ELISA on culture supernatants, CT production by P' and P. strains was equivalent.…”

Genetics of Vibrio cholerae and its bacteriophages.

“…This is thought to be due to a decreased production of cholera toxin. The original observations have been confirmed by using temperaturesensitive derivatives of P, which, when present, result in about a 10-fold reduction in cholera toxin production (63).…”

Waterborne transmission and the evolution of virulence among gastrointestinal bacteria

“…Virulence depends directly on the presence of genes for adhesiveness, toxin production, and invasiveness and other genes which regulate or complement these characteristics [105,303,[304][305][306][307][308][309].…”