Fig 4. Increased Ply release observed upon murMN deletion can be differentially restored by variant murMN alleles.

Hemolytic activity of whole cells (A) or sonicated lysates (B) of marked ΔmurMN strains expressing the murMN operon from wt (murMN ^TIGR4), R36A (murMN ^R36A) or Pen6 (murMN ^Pen6). The wt chromosomal murMN promoter controls expression of each allele. Data are presented as the mean fold change in hemolytic activity compared to the wt in each condition ± SEM of at least four biological replicates. * p < 0.05, Student’s t-test. (C) RP-HPLC analysis of the stem peptides from purified PG isolated from each of the repaired strains. See Materials and Methods for a description of the procedures for PG purification, separation of stem peptides, and analysis. Peptides were detected by their absorption at 210 nm and the chemical structures of assigned peaks are diagrammed in S4 Fig.