Fig. 7.

Subtoxic level of hok increases tolerance of stationary-phase E. amylovora cells to streptomycin. Single colonies of E. amylovora cultures were grown in LB broth amended with selective antibiotics for 20 h to reach stationary phase. Cultures were washed twice using fresh LB broth before streptomycin was added to 100 μg/ml; the culture was subsequently incubated at 28 °C with shaking for 5 h. Survival rate was determined as the ratio of CFU/ml after the treatment to that before the treatment. Arabinose at 10 mM and no IPTG was supplemented into the cultures. Results represent the means of four biological replications and error bars indicate the standard deviation. Asterisk symbols indicate significant differences (P < 0.05 using Student’s t-test). The assays were done three times with similar results