AUTOLYSIS AND CELL-WALL DEGRADATION IN A CHOLINE-INDEPENDENT STRAIN OF STREPTOCOCCUS-PNEUMONIAE

Streptococcus pneumoniae has an auxotrophic requirement for choline, a nd choline residues that incorporate into the wall and membrane teicho ic acids are intimately involved with the control of autolytic phenome na of this bacterium, We report here the re-examination of the role of choline in autolytic cell wall degradation using the choline-independ ent S. pneumoniae strain R6Cho(-) recovered from a heterologous cross with DNA from Streptococcus oralis. S. pneumoniae Cho(-) cultured in c holine-free medium grew with normal generation time but formed long ch ains, failed to undergo stationary-phase autolysis, and was also resis tant to lysis induced by deoxycholate or penicillin, Cell walls produc ed under these conditions had reduced phosphorus content, contained no choline residues detectable by nuclear magnetic resonance, and had re duced binding capacity for the pneumococcal autolytic amidase, and com plete hydrolysis of such walls by the amidase required prolonged incub ation with high concentrations of the enzyme, Addition of choline to t he growth medium reversed all these phenomena, High-performance liquid chromatography analysis of amidase digests of cell walls prepared fro m strain R6Cho(-) grown with or without choline produced identical ste m peptide profiles, which were also similar to that of the parental S. pneumoniae strain R6. Peptidoglycans prepared by hydrofluoric extract ion of cell walls from Cho(-) growth with or without choline or from t he parental strain R6 were uniformly susceptible to the autolytic amid ase and were fully degraded to the normal family of stem peptides, ind icating that, in sharp contrast to the case of cell walls, the amidase degradation of teichoic acid-free peptidoglycan did not require the p resence of choline residues in the substrate.