ABSTRACT
The effect of O2 and CO2 on expression of toxic shock syndrome toxin 1 (TSST-1) by Staphylococcus aureus was investigated under controlled growth conditions 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 specific TSST-1 (expressed as micrograms per milligram of cell dry weight) was 5.9-fold greater at an O2concentration of 4% than under anaerobic conditions. Increasing the O2 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% O2 but did result in a significant increase (4.9-fold; P < 0.001) in the rate of toxin production over that during anaerobic growth. At at
d of 9 h, addition of 3.5% O2 resulted in a 7.6-fold increase in specific TSST-1 production. When room air was sparged through a culture growing at at
d of 9 h, TSST-1 production increased significantly (by 3.4-fold) over that during anaerobic growth. When a growth environment of 4% O2–remainder N2 was studied, no increase in TSST-1 production was observed; this was also the case with 8% O2 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 O2 was metabolized by S. aureus. Addition of CO2 to the gas mix (4% O2, 10% CO2, 86% N2) resulted in a 5.1- to 6.8-fold increase in TSST-1 production over that during anaerobic growth and a 3.6-fold increase over that during growth in an environment of 4% O2–remainder N2. The agr mutant strain tested produced 6.1-fold more specific TSST-1 in a growth environment of 4% O2–10% CO2–86% N2 than during anaerobic growth. These data suggest that in this system, O2 alone does not trigger production of TSST-1; rather, both CO2 and O2 are required.
Impact of anaerobic growth conditions on toxic shock syndrome toxin-I production byStaphylococcus aureus
