BIOLOGICAL PROPERTIES OF EXTRACELLULAR PROTEINS FROM STAPHYLOCOCCUS *

Strains of Staphylococcus aureus release a large number of extracellular enzymes and toxins into their environment during growth in vivo and in vitro. Bernheimer and Schwartz found that 12 to 14 different proteins from potentially pathogenic strains could be separated by analytical starch gel electrophoresis, while about half as many were found in the culture supernatant fluids from nonpathogenic strains. More recent studies by isoelectric focusing in gel revealed that quite different patterns are produced by different strains of Stuphylococcus aureus (FIGURE 1 ) . Strain M18, which is a potent producer of several toxins and enzymes,3,=‘ and strain Smith 5R5 were found to give as many as 25-30 bands in these gels, while strain V8 gave only 4-10 bands (FIGURE 1 ). Analysis of these proteins by cross-immunoelectrophoresis with a polyvalent commercial antiserum also revealed that S. aureus strain M18 gave 18-20 different rocketlike immunoprecipitates (FIGURE 2 ) . The most remarkable finding in these studies, however, is the complex pattern obtained with S. epidermidis strain 129, which clearly indicates that several of the extracellular antigens in these two species are probably the same (FIGURE 2 ) . More extensive investigations of over 100 strains of S. aureus and S . epidermidis are in progress, but it is already evident that strains of S. epidermidis and nucleasepositive, coagulase-negative strains of Staphylococcus 6 also produce different protein patterns when analyzed by this technique (FIGURE 1 ) . This method might be useful in the future for more extensive taxonomical studies, with special reference to the biotypes 1 to 3 (TABLE I ) , which in our opinion cannot be differentiated as either S. aureus or S. epiderrnidis.G9 It is remarkable that no more analytical studies on the total number of extracellular proteins of the Staphylococcus have been reported. Besides the classical toxins and enzymes listed in TABLES 2 and 3, recent work in several laboratories has shown that new toxins such as the epidermolytic toxin,”I0 succinate oxidase factor,” and lymphocyte mitogens l2 can be discovered. Further investigations may reveal more new proteins with interesting biological effects; they may also show that an analytical tool such as gel electrofocusing,Z, l3 and this technique used in combination with immunodiffusion or zymogram methods to detect biological activities directly in the gel after separation,15 may be helpful in selecting strains for such studies. li reported that Group