The Characteristics of Extracellular Protein Secretion by Staphylococcus aureus (Wood 46) and their Relationship to the Regulation of -Toxin Formation

Abstract

The progress of secretion of .alpha.-toxin and total extracellular protein by S. aureus (Wood 46), grown aerobically at 37.degree. C, in a 3% (wt/vol.) tryptone soya broth medium supplemented with vitamins was followed. Exoprotein was secreted at a high rate by intact bacteria during the exponential phase (to 9 h) and into the post-exponential phase. After 18 h, when exoprotein accounted for 33% of the total protein in the culture, no further exoprotein was secreted although the bacterial density continued to increase at a low rate beyond this time. During the phase of active secretion, .alpha.-toxin represented a constant proportion of total exoprotein, the differential role of synthesis of which increased by a factor of 4 after the end of exponential growth. Concomitant with the increase in the differential rate of exoprotein formation there was a 4-fold increase in the intracellular concentration of RNA precursor material.