Factors affecting the regulation of staphylococcal enterotoxin B

Several factors which regulate the synthesis of enterotoxin B were examined in Staphylococcus aureus S-6 and in its heme-requiring mutant S-6H2. The kinetics of enterotoxin B synthesis during anaerobic growth were identical to those observed under aerobic conditions; extracellular enterotoxin accumulated in the medium during the transition between exponential and stationary phase growth. Strain S-6H2 lacked a functional electron transport system unless the medium was supplemented with heme. In a casein hydrolysate medium, the presence or absence of a functional electron transport system had no effect upon the differential rate of toxin synthesis. The repression of toxin synthesis by glucose at either pH 6.0 or 7.7 or by pyruvate at pH 7.7 occurred in the absence of a functional electron transport system, but was enhanced significantly in its presence. Thus, a functional electron transport system appears to be involved in regulating the degree of glucose and pyruvate repression of enterotoxin B synthesis.