Characterization of the sigma(B) regulon in Staphylococcus aureus

The sigma (B)-dependent stress regulon in gram-positive bacteria might fulf ill a physiological role in stress response and virulence similar to that o f the sigma (S) regulon in Escherichia coli and other gram-negative bacteri a. in order to obtain evidence for the function of the sigma (B) regulon of Staphylococcus aureus, especially in virulence control, sigma (B)-dependen t stress genes were identified. The two-dimensional protein pattern of wild -type cells of S. aureus COL was compared with that of an isogenic sigB mut ant. By this approach, we found that the synthesis of about 27 cytoplasmic proteins seemed to be under the positive control of sigma (B). N-terminal s equencing of 18 proteins allowed the identification of their genes on the a lmost finished genome sequence of S, aureus COL and the analysis of the pro moter structure. Transcriptional analyses of II of these genes confirmed th eir sigma (B) dependency, and moreover, about 7 additional sigma (B)-depend ent genes were found which are cotranscribed with the newly detected genes, forming operons, Altogether, we identified 23 sigma (B)-dependent genes an d their corresponding proteins, Among them are proteins probably involved i n the generation of NADH or in membrane transport mechanisms, Furthermore, at Least one clpC-homologous gene was localized on the S, aureus sequence s olely transcribed by sigma (B). In contrast, a second clpC-homologous gene in S, aureus forming an operon with ctsR, yacH, and yacI was sigma (B) inde pendently expressed.