The Spontaneous Release of Somatic Antigen from Vibrio cholerae

Department of Microbiology, The University of Texas Southwestern Medical School, Dallas, Texas 75235, U.S.A. ABSTRACT Culture supernatants of Ogawa and Inaba strains of Vibrio cholerae contained, judging by their ability to inhibit the vibriocidal action of homologus The release of antigen was readily detectable during the exponential phase of growth. The release of antigen was not entirely dependent on cell lysis or death, nor was the decrease in the pH of the medium during the early phase of growth responsible for antigen release. As the concentration of antigen increased, protein, carbohydrate and 260 nm-absorbing material increased in dialysed supernatants but an intracellular enzyme, malate dehydrogenase, was not detectable up to 40 h growth. The antigen demonstrable in supernatants at 40 h accounted for more than a third of the total capacity of the cultures to inhibit vibriocidal antibody. Ethylenediaminetetra-acetate not only increased the release of antigen in suspensions of agar-grown vibrios but also released intracellular substances. Supernatants of Ogawa cultures were distinctly more inhibitory than Inaba supernatants but both were equally effective in gel diffusion precipitation.