SUMMARY: The production of enterotoxins, lipase and total extracellular protein by four strains of grown in batch culture at a controlled pH of 6.5 in a completely defined medium was markedly reduced by glucose or glycerol constantly maintained at 0.1 M. A concomitant increase in the production of deoxy-ribonuclease, up to 13-fold, showed however that not all extracellular proteins are under the same control mechanism. The presence of glucose and glycerol in the medium also resulted in a rapid increase in the specific growth rate. However, growth of s6 in Mg-limited continuous culture showed that glucose repression of enterotoxin B when the growth rate was held constant was more than twice that in batch culture. Therefore glucose repression can occur independently of an increase in growth rate. The specific rate of production of enterotoxin B, lipase, deoxyribonuclease, β-haemolysin and total extracellular protein by s6 increased as the growth rate increased from 0.07 to 0.24 h. Non-replicating cells grown in the absence of glucose produced considerable amounts of enterotoxin, and production was not repressed by the presence of glucose in the re-suspension medium. In contrast, no enterotoxin B or C was obtained from non-replicating cells grown in the presence of glucose. Chloramphenicol completely inhibited enterotoxin production by non-replicating cells, indicating that synthesis of new protein was required.


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