The development of a new semisynthetic medium which stimulates in vitro production of the skin permeability factor (PF) by Vibrio cholerae is described. The effects of pH, aeration, temperature, and length of incubation on PF formation or release in strain 569B and several other strains, or both, are compared. Data are presented which show that maximal PF accumulation occurs during a transitional period of growth joining the exponential and stationary phases of the growth cycle. PF elaboration is completed well ahead of any visible signs of lysis in the culture and the PF activity appears to be proportional to the length of the linear growth phase. Possible mechanisms of toxigenicity and the nature of PF are discussed.
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