Figure 5: m¹G37 deficiency decreases resistance and persistence to antibiotic treatment.

A-C) Resistance arises less frequently in m¹G37− (red) E. coli (A) and Salmonella (B) trmDKD cells than in m¹G37+ (blue) cells. An overnight culture of cells at 10⁵ CFUs was plated onto an LB agar plate containing the indicated concentration of gentamicin (Gen), kanamycin (Kan), ampicillin (Amp), or vancomycin (Van). Each concentration was near 1X MIC for m¹G37+ cells. Resistant colonies were counted after incubation at 37 °C for 3 days. Mutants were verified to have an increase in MIC to the respective antibiotic (C). Data and error bars are mean ± SD, n = 3. Welch’s t-test: *p < 0.1, **p < 0.05, ***p < 0.01.

D-F) Persistence of Salmonella trmD-KD cells, showing CFUs/mL over time (left) and the average CFUs/mL at 6 h post-treatment in m¹G37+ and m¹G37− conditions (right). Untreated Salmonella trmD-KD cells had similar CFUs/mL in the two conditions (D), while persistence arose more frequently in m¹G37+ than m¹G37− cells treated with 20 μg/mL Gen (3.7X and 8.5X MIC for m¹G37+ and m¹G37− conditions) (E) and with 100 μg/mL paromomycin (Par; 2.7X and 10.7X MIC for m¹G37+ and m¹G37− conditions) (F). An overnight culture in LB with 0.2% Ara was diluted 1:100 into fresh LB with or without 0.2% Ara and incubated at 37 °C for 3 h. Cells were treated with water (no drug), Gen or Par for 0, 1, 2, 4, and 6 h, collected, washed, and plated on LB with Ara. Horizontal lines on the right represent the median, n = 5. Mann-Whitney U test: **p < 0.05, ***p < 0.01.