Figure 5. Gonococcal survival assays.

A. Survival after exposure to H₂O₂. The parental, phrB mutant (PhrB−) and complement strains were exposed to 0, 10, 20, 50 mM H₂O₂. Error bars represent the standard error of the mean of five-six independent experiments. The phrB mutant (PhrB−) is more sensitive than the parental strain when exposed to 10 and 20 mM H₂O₂ as measured by Student’s t-test, P<0.05 (asterisks). B. Nalidixic acid survival assay. Nalidixic acid is a compound that inhibits DNA gyrase and causes DNA double strand breaks (Zhao et al., 1997, Cozzarelli, 1980). The parental, phrB mutant (PhrB−), and complement strains were grown on media containing 0.8 ug/ml nalidixic acid. Bars represent the median of seven independent experiments where each experiment had five replicates. The phrB mutant is different from the parental strain as measured by Student’s t-test, P<0.05 (asterisks). C. Rifampicin survival assay. Rifampicin inhibits transcription by binding to the β-subunit of DNA-dependent RNA polymerase (Nolte et al., 2003). The parental, phrB mutant (PhrB−), and complement strains were grown on media containing a level of rifampicin (30 ng/ml), which allows survival to be measured. Bars represent the median of five independent experiments where each experiment had five replicates. The phrB mutant is different from the parental strain as measured by Student’s t-test, P<0.05 (asterisks).