The bacteriolytic agent lysostaphin has been isolated from the culture supernatant of Staphylococcus epidermidis, NRRL B-2628 (K-6-W1) on the ion-exchange resin Amberlite IRC-50. A salt gradient released three enzyme specificities which were further purified to apparent homogeneity. These enzymes, belonging to three different classes, were endo-p-N-acetylglucosaminidase, endopeptidase (glycinase) and N-acetylmuramyl-L-alanine amidase. I n contrast to the first two enzymes, the third one was not found to be bacteriolytic per se.Bacteriolysis or solubilization of mucopeptide networks, the basic structure of all bacterial cell walls, can be brought about by three classes of enzymes. These are enzymes that (a) hydrolyse the polysaccharide chains (glycosidases or hexosaminidases), enzymes that (b) split the bond within the peptides and their cross-links (endopeptidases) or enzymes that (c) cleave the junctions between polysaccharides and peptides (acetylmuramyl-L-alanine amidases) [l-31.

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Tryptic digests of acid‐treated Fc from normal human IgG were separated into four peaks (I to IV) by gel filtration on Sephadex G‐100. Essentially all the material from peak I reacted with staphylococcal protein A. had a molecular weight (MW) of approximately 55,000, and was indistinguishable from intact Fc on electrophoresis and immunodiffusion. Peaks II and III, MW 42,000 and 32,000. respectively, contained both protein A‐reactive and protein A‐nonreactive material, whereas peak IV. MW 12,000, showed no reaction with protein A The protein A‐reactive material from peaks II and III had an intact Fc chain bound to another peptide, from which a part of the C‐terminal sequence had been removed. The protein A‐nonreactive material from peaks II and III lacked antigenic determinant(s) compared to intact Fc and gave fragments with MWs of 16.000 and 18,000. respectively, after reduction, suggesting that these fragments consist of Fc N‐terminal sequences joined by disulfide bonds. It is concluded that, in contrast to interchain interaction, intrachain interactions influence protein A activity.

Immunoperoxidase technique together with electron microscopy shows that lipoteichoic acid (LTA) of Staphylococcus aureus Cowan I is attached to the membrane and penetrates the whole cell wall. A diffuse zone outside and no peroxidase reaction product inside the wall when whole cells were treated with antibody prior to embedding may indicate (i) that LTA is exposed to reaction with antibodies outside the wall, and (ii) that all or most of the anti‐LTA antibodies used are of the IgM class and thus unable to penetrate the wall. Thin sections of strain Wood 46 showed the same picture as Cowan I, but treatment of whole cells before embedding gave no diffuse zone outside the wall. This may be due to a thicker wall as found by electron microscopy and/or shorter LTA‐chains of strain Wood 46 than those present in the wall of Cowan I.

The immunoperoxidase technique together with electron microscopy has been examined for the ultrastructural localization of staphylococcal protein A, the immunoferritin method being included for comparison. The results show that protein A is uniformly distributed in the whole cell wall. Both the direct and indirect methods, Fab‐ as well as Fc‐reactions, showed identical results. The immunoperoxidase method was superior to the immunoferritin method, especially when applied to thin sections of the bacteria, and the clear specificity demonstrated indicates a useful method for localization of cellular antigens.

Mucopeptides from one Staphylococcus aureus, two Staph. epidermidis and two Micrococcus strains have been prepared and examined for chemical composition and for serological activity. The chemical analyses showed differences in the mucopeptide structures, especially between staphylococci and micrococci, some differences appearing to be related to variations in the inter‐peptide bridges. No precipitation was observed, but agglutination was obtained in antisera to whole bacteria as well as in antisera to mucopeptides. Cross‐absorption studies showed the presence of shared and specific antigenic determinants. None of the mucopeptides sensitized erythrocytes for agglutination in antisera, but the staphylococcal mucopeptides, in contrast to the micrococcal, induced the production of haemagglutinins in rabbits. Antibodies to mucopeptides were found in human serum and colostrum. The sera contained antibodies of the IgG class; colostrum mostly IgA antibodies. Sera with increased anti‐staphyiolysin titres contained higher amounts of IgG than normal sera. Fab but not Fc fragments of IgG were found to bind to mucopeptide, and complexes of mucopeptide and IgG fixed complement. Injection of mucopeptides into rabbit and human skin provoked dermonestronic reactions.

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Purified polysaccharides were isolated from coagulase‐positive staphylococci of pigeon, dog and swine origin. In agreement with previous serologic findings in whole bacteria, three types of cell wall polysaccharides were demonstrated according to their serologic and chemical characteristics. Each polysaccharide produced one specific precipitation line in agar gel. Poly H (pigeon) seemed to be a glycerol teichoic acid containing β‐glucosamine as the antigenic determinant. Poly P (dog) and poly V (swine) apparently had rather complex and unusual structures. Both were polyglycerophosphates and two, respectively four, sugars were detected.