EXTRACELLULAR ANTIGENS IN STEADY-STATE CULTURES OF THE HEMOLYTIC STREPTOCOCCUS: PRODUCTION OF PROTEINASE AT LOW pH

Abstract

[beta]-Hemolytlc streptococci have been grown in a steady-state by continuous dilution of the culture at constant volume, using a chemically defined medium. Concentrated supernatants of cultures grown at a pH range of 6.0-6.3 contained, in relatively high concentration, one of the proteins present in similar concentrates from conventional bulk cultures. Some properties of the chief component of the low-pH cultures were determined, and these suggested its identity with the streptococcal proteinase described by Elliott. Repeated precipitation with ammonium sulfate near the isoelectric point of the proteinase or application of the proteolytic property of this substance resulted in approximately similar degrees of relative purification of the proteinase. Applications of one-dimensional gel precipitation are described for identifying a constituent of a mixture of antigens with the same substance identified by other means (in this case, paper electrophoresis) and for estimating changes in the degree of relative purification of one constituent in a mixture of antigens.