Studies of the receptor for phage A25 in group A streptococci: the role of peptidoglycan in reversible adsorption.

Abstract

The first step in the life cycle of a bacteriophage is its attachment to an outer surface of the bacterial cell. In gram-positive bacteria the cell wall peptidoglycan, or this molecule complexed with other macromolecules, often serves as the phage receptor (1). Previous reports have suggested that the group-specific carbohydrate may play a role as receptor site for the virulent group A streptococcal phage, A25. The inhibition of adsorption by group A antisera and the inability of group A variant cells to adsorb phage A25, provided indirect evidence supporting this view (2). Direct evidence, the isolation and characterization of the receptor site, was not obtained because heat-killed or mechanically disrupted cells failed to inactivate phage particles irreversibly, even though the potential to adsorb this phage reversibly was retained (2, 3).Because it is now clear that phage A25 can infect and transduce antibiotic resistance between different groups of streptococci, such as groups C and G, it seemed essential to identify the phage A25 receptor in group A organisms (4-6). In contrast to earlier reports, the findings reported here demonstrate the irreversible attachment of phage A25 to heat-killed group A, G, and A-variant cells. The complexity of the adsorption process is exemplified by the fact that mechanical disruption of heat-killed cells completely destroyed the irreversible nature of this process. Receptors for the reversible attachment of phage A25 survive mechanical disruption, and experiments including electron microscopy are described which demonstrate the specificity of reversible adsorption and identify the responsible receptor as peptidoglycan. The evidence suggests that adsorption of phage A25 to group A streptococci occurs in a two-step reaction, the first step is the reversible attachment of the phage tail to peptidoglycan exposed on the cell surface, followed by the irreversible inactivation of the phage particle. The latter is still not understood. Materials and MethodsBacterml Strains and Bactermphages. The virulent phage designated A25 was originally described and kindly supphed by Dr. W. R. Maxted (7,8). This virulent phage was used for all adsorption experiments and has been further described by Malke (5) and Read and Reed (9).

Genetic modifications to temperate Enterococcus faecalis phage ϕEf11 that abolish the establishment of lysogeny and sensitivity to repressor, and increase host range and productivity of lytic infection

“…O-acetylation of the lipopolysaccharide side chains, changes in the bonding between the lipopolysaccharide trisaccharide units from a1A4 to b1A4) on the host cell, resulting in the inability of the cell to adsorb additional phage. Although the previous examples of phage receptor modification involve Gram-negative bacteria, it is possible that a similar phenomenon may occur in E. faecalis as the phage receptors in most Gram-positive, low G+C bacteria are cell surface polysaccharides (Vidaver & Brock, 1966;Douglas & Wolin, 1971;Cleary et al, 1977;Yokokura 1977;Keogh & Pettingill, 1983;Valyasevi et al, 1990;Schäfer et al, 1991). If this is the case, then evolutionarily speaking, it may be that originally E. faecalis TUSoD11 was nonlysogenic and possessed cell-surface phage receptors.…”

Differential Recognition of Surface Proteins inStreptococcus pyogenesby Two Sortase Gene Homologs

“…The cell wall cross-bridges of these organisms are virtually identical (56), and it seems likely that the peptidoglycan structure is also similar. The muralytic lysin enzyme from phage A25 is active on the cell walls of group A, C, and G streptococci (22), and group A and C streptococci have been shown to possess the receptor for phage A25 (9). Similarly, group A and C streptococci are sensitive to the C1 phage lysin (45).…”

An Electron Microscopic Study of the Location of Peptidoglycan in Group A and C Streptococcal Cell Walls

“…The streptococci used for these experiments were free of Fc-binding factor (Christensen et al, 1976), since the presence of Fc-binding factor disturbed the specificity of the antibody binding. By phage-adsorption experiments Cleary et al (1977) have shown that at least part of the peptidoglycan is located at the coccal surface. Similar results has been obtained by means of the immunofluorescence technique on B. licheniforrnis cells (Hughes & Stokes, 1971).…”