GROUP-SPECIFIC CARBOHYDRATE OF GROUP C-VARIANT HEMOLYTIC STREPTOCOCCI

Cell wall polysaccharides of Gram positive ovococcoid bacteria and their role as bacteriophage receptors

Gram-positive bacterial cell walls are characterised by the presence of a thick peptidoglycan layer which provides protection from extracellular stresses, maintains cell integrity and determines cell morphology, while it also serves as a foundation to anchor a number of crucial polymeric structures. For ovococcal species, including streptococci, enterococci and lactococci, such structures are represented by rhamnose-containing cell wall polysaccharides, which at least in some instances appear to serve as a functional replacement for wall teichoic acids. The biochemical composition of several streptococcal, lactococcal and enterococcal rhamnose-containing cell wall polysaccharides have been elucidated, while associated functional genomic analyses have facilitated the proposition of models for individual biosynthetic pathways. Here, we review the genomic loci which encode the enzymatic machinery to produce rhamnose-containing, cell wall-associated polysaccharide (Rha cwps) structures of the afore-mentioned ovococcal bacteria with particular emphasis on gene content, biochemical structure and common biosynthetic steps. Furthermore, we discuss the role played by these saccharidic polymers as receptors for bacteriophages and the important role phages play in driving Rha cwps diversification and evolution.

IMMUNOCHEMICAL STUDIES ON THE SPECIFIC CARBOHYDRATE OF GROUP G STREPTOCOCCI

Group G hemolytic streptococcal cell walls which have been treated with trypsin are composed of a group-specific polysaccharide moiety and a mucopeptide matrix. The mucopeptide contains N-acetylglucosamine, N-acetylmuramic acid, alanine, glutamic acid, lysine, and glycine, a composition similar to that of other groups of streptococci. The Group G carbohydrate is composed of rhamnose, N-acetylgalactosamine, and galactose. Serological studies suggest that the monosaccharide of L-rhamnose is a major component of the determinant of antigenic specificity.

ANTIGENIC RELATIONSHIPS BETWEEN GROUPS B AND G STREPTOCOCCI

Trypsinized cell walls of Group B hemolytic streptococci are composed of a group-specific carbohydrate and mucopeptide. The carbohydrate extracted with hot formamide is composed of rhamnose, N-acetylglucosamine, and galactose. Quantitative precipitin inhibition studies have shown that L rhamose is the significant component of the antigenic determinant. The cross-reactivity between B and G carbohydrates is dependent upon the fact that Lrhamose is a determinant sugar in both antigens.

Characterization of the serotype e polysaccharide antigen of Streptococcus mutans

The structure of the Streptococcus mutans serotype e polysaccharide was studied in order to determine the chemical basis of the immunological cross-reactions observed between it and the streptococcal group E polysaccharide. The chemical structure was established using methylation analysis, periodate oxidation, partial methanolysis and 13C NMR spectroscopy. The polysaccharide was found to consist of a polyrhamnose backbone of alternating 2- and 3-linked alpha-L-rhamnose units and sidechain beta-D-glucosyl units linked to the 2-position of rhamnose units in the backbone. This structure of the oligosaccharide repeating unit of the S. mutans serotype e polysaccharide was identical to that of the group-specific polysaccharide of group E Streptococcus. Possible explanations for the previously reported differences in these two polysaccharides are discussed.

Immunochemical analysis of streptococcal group A, B, and C carbohydrates, with emphasis on group A

Streptococcal group A, B, and C carbohydrates were analyzed by counterimmunoelectrophoresis, immunoelectrophoresis, and inhibition of immunoprecipitation. Extracts of streptococci group A or C were shown by counterimmunoelectrophoresis to contain both anodic and cathodic migrating components. In immunoelectrophoresis, group A and C substances formed a continuous precipitation line stretching from the anode to the cathode, suggesting a heterogeneous population of molecules with immunochemical identity. This identity was confirmed by inhibition of immunoprecipitation, in which both anodic and cathodic immunoprecipitates were inhibited by the same constituent sugars: group A-anti-A was inhibited by N-acetylglucosamine, and group C-anti-C was inhibited by N-acetylgalactosamine. Extracts of group B showed only anodic migration in counterimmunoelectrophoresis and a narrow, anodic arc in immunoelectrophoresis. The group B-anti-B reaction was inhibited by rhamnose. Carbohydrates of variant strains of group A streptococci were also analyzed by the same methods. The results suggest that the heterogeneity of group A carbohydrate may have resulted from attachment of various amounts of N-acetylglucosamine to the polyrhamnose backbone.

The presence of a group A variant-like antigen in streptococci of other groups with special reference to group N

A Group A variant-like antigen has been detected in streptococci belonging to Groups D, E, G, M, and N. In Groups D and N the variant-like antigen was located in the streptococcal cell walls. In two strains of Group N streptococci (C559 and B209) the cell walls were chemically different and serologically distinct. In strain C559 N-acetylgalactosamine, and in strain B209, N-acetylglucosamine were the major determinants of serological specificity. The cell walls of strain C559 contained at least three serologically reactive components: a rhamnose-containing fraction that precipitated with an antiserum to Group A-variant carbohydrate; a strain-specific polysaccharide composed of galactosamine and glucosamine, both in the N-acetylated form and probably polymerized with an unidentified phosphorylated substance; and a component of unknown composition serologically related to a Group D streptococcus strain C3 (S. durans). An analogy is drawn between the cell wall structure in streptococcus and Salmonella.

The bacterial induction of homograft sensitivity. II. Effects of sensitization with staphylococci and other microoorganisms

Heat-killed strains of Staphylococcus aureus and Staphylococcus albus can induce in guinea pigs a state of altered reactivity to skin homografts which is indistinguishable from that which results from sensitization with homologous tissues or Group A streptococci. Challenge of suitably prepared recipients with first-set skin homografts obtained from unrelated randomly selected donors elicits white graft reactions or accelerated rejection of such grafts. Other bacteria tested included Lancefield streptococcal groups B, C, D, E, G, H, L, and O, pneumococcus Types II, III, XIV and a rough strain, Corynebacterium xerosis, Bacillus subtilis, Escherichia coli, Aerobacter aerogenes, Salmonella typhimurium, Proteus vulgaris, Neisseria catarrhalis, Haemophilus influenzae, and two human virulent strains of Mycobacterium tuberculosis. None of these microorganisms was active in the induction of homograft sensitivity in the guinea pig. Pretreatment of recipients with Gram-negative bacterial suspensions was associated with a slight increase in the mean survival time of first-set skin homografts. Results of this study suggest the presence in staphylococci, as well as in Group A streptococci, of antigens related in their biologic effects to tissue transplantation antigens.