A. Severin et al., AUTOLYSIS AND CELL-WALL DEGRADATION IN A CHOLINE-INDEPENDENT STRAIN OF STREPTOCOCCUS-PNEUMONIAE, Microbial drug resistance, 3(4), 1997, pp. 391-400
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.