Infection and Immunity, September 2000, p. 5205-5209, Vol. 68, No. 9
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Departments of Medicine1 and Pathology,2 Channing Laboratory, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
Received 22 February 2000/Returned for modification 21 March 2000/Accepted 26 June 2000
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 (td)
of
3 h, production of specific TSST-1 (expressed as micrograms per
milligram of cell dry weight) was 5.9-fold greater at an O2
concentration 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 a
td 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 a
td 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.
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