Figure 2.

Expression of the hly_II operon of J96 is derepressed by a mutation in the zur gene. (a) Lac-phenotype on LB Xgal agar plates of the JFV3 (J96 hly_II::lacZ) strain and its Gm^R derivative (clone #13) obtained by random mutagenesis. Below is represented the location of the Gm^R transposon insertion in clone #13. (b) Transcriptional expression of the hly_II operon from cultures of the JFV3 strain and the two derivatives zur::Gm^R (clone #13) and zur::Cm^R (EV46) grown in LB at 37 °C up to late-log phase (OD_600 nm of 1.0). β-Galactosidase activity (Miller units) was determined in three independent cultures. Mean values with standard deviations are plotted. *P < 0.05, ANOVA with Tukey’s multiple comparisons test. (c) Electrophoretic analysis of secreted protein extracts from cultures grown in LB at 37 °C up to late-log phase of J96, JFV16 (J96ΔII) and JFV21 (J96ΔI) strains and their otherwise isogenic zur::Cm^R mutants (EV27, EV34 and EV38, respectively). Upper panels are Coomassie blue stained 10% SDS-PAGE and lower panels immunodetection using monoclonal anti-HlyA antibody. Samples for immunodetection from J96ΔII were concentrated 20x with respect to rest of samples for better visualization. Full-length gel and blot images are shown in Fig. S7. (d) Hemolytic phenotype of JFV16 (J96ΔII) and JFV21 (J96ΔI) strains and its zur mutant derivatives on Columbia Blood agar plates.