Fig. 1

Spontaneous mutation frequency in N. gonorrhoeae mutants with disrupted ngoAXIIIV, ngoAXIVV, mutL_Ngo or mutS genes. A sample of liquid culture (0.1 ml, 10⁸ cells) of each strain was plated on GC agar supplemented with rifampicin or without antibiotics. After incubation at 37 °C in 5% CO₂ for 48 h, the colony numbers were counted and frequency of spontaneous mutations causing rifampicin resistance determined. Asterisks indicate statistically significant differences compared to wild-type strain, which were calculated using the two-tailed heteroscedastic Student’s t-test (p value < 0.05)