Enterotoxin B synthesis by replicating and nonreplicating cells of Staphylococcus aureus

Abstract

Although 95% of the enterotoxin B produced by Staphylococcus aureus appears during the latter part of the exponential phase of growth, growth per se is not necessary for toxin synthesis. A procedure is described whereby a concentrated suspension (at least 6 x 10(10) cells per ml) of a 16-hr culture of S. aureus was found to be capable of producing toxin, without replication, when air and glucose were present. This technique allows the growth requirement to be separated from toxin formation. Although higher (100 mug/ml) concentrations of toxin appeared in the medium when nitrogen was present, lower levels (30 mug/ml) were produced in the absence of N-Z-amine A. Toxin production proceeded without any net increase in deoxyribonucleic acid, ribonucleic acid, or protein. Chloramphenicol did not inhibit toxin formation in a nitrogen-free medium. The optimal pH for toxin production in a nitrogen-free medium was 8.0 to 8.5; for synthesis in a medium where nitrogen was available, the optimal pH was 7.0 to 7.5. Increasing the rate of aeration increased toxin release during growth, but decreased the amount of toxin subsequently produced when the bacteria were resuspended. These results suggest the presence of a precursor pool in the cells collected after 16 hr of growth.