The effect of temperature on the growth of Staphylococcus aureus. A method was developed to study the effect of temperature on the growth of Staphylococcus aureus. When grown aerobically at 37 degrees C, S. aureus entered a stationary phase when the growth rate fell to zero. The change from logarithmic to stationary phase occurred over a period of 3 to 4 h. The rate of growth and the stationary-phase density of a culture could not be measured by measuring OD at a single wavelength. An assay was developed in which at least two OD readings were recorded at different wavelengths and the change in OD was calculated. At 37 degrees C this change in OD correlated with the growth rate (r2 greater than 0.99), whereas at any other temperature OD did not correlate with growth rate (r2 less than 0.90). To study the effect of temperature on the duration of the exponential phase and growth rate, cultures were grown in a glucose broth at various temperatures. Temperature showed no effect on the duration of exponential phase and only a small effect on growth rate in the range 25 degrees to 42 degrees C. It was concluded that growth rate was independent of temperature in the range studied. These results explain why at 37 degrees C, where growth rate is zero, Staphylococcus aureus enters stationary phase in 3 to 4 h and ceases growth with the cessation of the exponential phase. In S. aureus grown at 42 degrees C, more rapid growth was observed and the stationary-phase density was lower than at 37 degrees C. The duration of the exponential phase was constant from 37 degrees C to 45 degrees C but declined at temperatures above 45 degrees C. The temperature had a greater effect on growth rate at 42 degrees C than at 44 degrees C, explaining why at higher temperatures the growth rate was higher than at 37 degrees C. The temperature limits for optimum growth and optimum growth rate were calculated. The optimum growth temperature was 37 degrees C. Growth rate was found to increase with increasing temperature, and the maximum was 3.8 X 10(-2) h-1 at 47 degrees C.