Production of toxic shock syndrome toxin 1 by Staphylococcus aureus requires both oxygen and carbon dioxide

The effect of O-2 and CO2 on expression of toxic shock syndrome toxin 1 (TS ST-1) by Staphylococcus aureus was investigated under controlled growth con ditions with continuous-culture techniques. To stimulate TSST-1 production, air and anaerobic gas were premixed before delivery to the culture vessel. At a growth rate-or mass doubling time (t(d))-of 3 h, production of specif ic TSST-1 (expressed as micrograms per milligram of cell dry weight) was 5. 9-fold greater at an O-2 concentration of 4% than under anaerobic condition s. Increasing the O-2 concentration to 11% did not result in a significant increase (P > 0.05) in the rate of toxin production over that during growth in 4% O-2 but did result in a significant increase (4.9-fold; P < 0.001) i n the rate of toxin production over that during anaerobic growth. At a t(d) of 9 h, addition of 3.5% O-2 resulted in a 7.6-fold increase in specific T SST-1 production. When room air was sparged through a culture growing at a t(d) of 9 h, TSST-1 production increased significantly (by 3.4-fold) over t hat during anaerobic growth. When a growth environment of 4% O-2-remainder N-2 was studied, no increase in TSST-1 production was observed; this was al so the case with 8% O-2 at gas-flow rates of 0.1, 0.2, and 0.4 liters/min. In all experiments, production of biomass (expressed as milligrams of cell dry weight per milliliter) increased, indicating that O-2 was metabolized b y S. aureus. Addition of CO2 to the gas mb (4% O-2, 10% CO2, 86% N-2) resul ted in a 5.1- to 6.8-fold increase in TSST-1 production over that during an aerobic growth and a 3.6-fold increase over that during growth in an enviro nment of 4% O-2-remainder N-2. The agr mutant strain tested produced 6.1-fo ld more specific TSST-1 in a growth environment of 4% O-2-10% CO2-86% N-2 t han during anaerobic growth. These data suggest that in this system, O-2 al one does not trigger production of TSST-1; rather, both CO2 and O-2 are req uired.