SUMMARY: Environmental conditions which might be present in the human intestinal lumen, such as anaerobiosis, a temperature of 37 and the presence of bile salts, were examined for their effects on the growth and toxin production by strains 569B and B1307 in Syncase and in peptone water media. Using aerobic conditions at 30 °, which are commonly used for enterotoxin production, toxin (5 μg ml1) and pleomorphic cells were detected during the exponential phase of the growth cycle. When the incubation temperature was raised to 37 °, no toxin (<0.1 μg ml) and no pleomorphic forms were found. In cultures incubated anaerobically at 30 or 37 °, the organisms grew poorly, forming pleomorphic cells which lysed after the cultures reached a maximum turbidity at 640 nm of 1.45 at 12 h. Toxin (2.5 μg ml-1) was present at 12, 24 and 48 h. When 0.1 % sodium deoxycholate was incorporated into the culture medium, growth was inhibited under aerobic conditions at 30 and 37 °. At 30 ° under aerobic conditions and at 37 ° under anaerobic conditions, the toxin yield was not significantly affected by the presence of sodium deoxycholate; but at 37 ° under aerobic conditions, sodium deoxycholate caused an increase in the toxin yield (5 μg ml) due to the release of cell-bound toxin.


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