Isolation and Characterization of Spontaneous Mutants of Staphylococcus aureus S6 Possessing Quantitative Differences in Enterotoxin B Production

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Spontaneous mutants possessing quantitative differences in enterotoxin B production were isolated from the parent strain of Staphylococcus aureus S6 by using NZ-amine agar plate which contained antienterotoxin B antiserum. A shake-flask culture of S. aureus S6 715H, a high enterotoxin B-producing strain, extracellularly produced 370μg/ml of enterotoxin B after 16hr of incubation at 37C. A shake- flask culture of S. aureus S6 715NH. a low enterotoxin B-producing strain, produced 22μg/ml of enterotoxin B under the same conditions. The difference in the ability to produce enterotoxin B among the strains resulted from differences in their activities of de novo enterotoxin B synthesis. A quantitative difference in the production of individual extracellular proteins existed in the strains. S. aureus S6 715H produced higher levels of α-and δ-hemolysins, alkaline phosphatase, ribonuclease and staphylokinase (fibrinolysin) than S. aureus S6 715NH. These results suggest that the production of enterotoxin B and most of the other extracellular proteins, at least the above five toxins or enzymes, may be dependent upon some coordinated control mechanisms in S. aureus S6.