The effect of glucose on the differential rates of extracellular protein and alpha-toxin formation by Staphylococcus aureus (Wood 46).

The differential rates of formation of total extracellular protein and alpha-toxin by Staphylococcus aureus (Wood 46) were determined during aerobic growth, at 37 degrees C, in a complex medium containing 0.0, 0.25 or 1.0% (wt/vol) glucose. Different inocula were employed from 1% (vol/vol) of an overnight culture to 100% where bacterial cells were washed and resuspended in fresh medium without change in density. It was shown that under all conditions examined the differential rates of total extracellular protein formation exhibited a biphasic pattern characteristic of regulation based on 'competition'. This biphasic pattern was maintained even in the presence of a large inoculum and a high glucose concentration, conditions considered to favour the onset of catabolite repression. However, a lowering of the initial rate was observed with increasing glucose suggesting the superimposition of catabolite repression as a modulating effect under extreme conditions. In the case of the specific extracellular protein component, alpha-toxin, its differential rate of formation paralleled total exoprotein in all except the condition most favourable for catabolite accumulation when a deviation consistent with a pronounced catabolite repression of this component was demonstrated which was not pH-dependent.