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

Concentrates of /3-hemolytic streptococcal culture filtrates have been shown by gel precipitation to contain at least 7 antigens, in recent studies by Halbert et al. (1955) and in this laboratory (Harris et al., 1955). Subsequently, electrophoretic analysis of concentrates of streptococcal culture supernatants also indicated the presence of a number of proteins in such preparations. In the course of experiments directed at the study of some properties of these proteins it became apparent that their relative concentration varied substantially among successive cultures. In the present study the conventional method of bulk culture used in the earlier work was replaced by the cultivation of 3-hemolytic streptococci under steady-state conditions in the chemostat, with the use of a completely defined medium. The chemostat provides a means of cultivating bacteria with continuous dilution of the culture at constant volume so that the pH and composition of the medium in which the cultivation of bacteria occurs are kept constant. Some characteristics of steady-state cultures of a strain of group A f3-hemolytic streptococei have been described elsewhere (Karush et al., 1956). In the present study culture supernatant concentrates were examined as obtained from steady-state cultivation of strain H44 (type 4) at pH values in the range of 6.8 to 5.95. Preliminary examination indicated that in the upper part of this range a number of proteins were produced at concentrations, relative to the total macromolecular material in such concentrates, which were below the threshold of detection by