Fig. 3: The regrowth-delay bodies are formed heterogeneously in the cell population and the degree of their formation correlates with the duration of regrowth lag and the level of multidrug tolerance.
From: Regrowth-delay body as a bacterial subcellular structure marking multidrug-tolerant persisters
a Fluorescence microscopic images of ftsZ-mNeonGreen cells cultured to the indicated time points in LB medium containing 0.02% rhamnose (to induce the production of FtsZ-mNeonGreen). Scale bars, 1 μm. b Percentage of cells containing regrowth-delay bodies that were cultured to the indicated time points. c Percentages of cells retaining their regrowth-delay bodies when the particular stationary-phase cell samples were re-cultured for 30 min in fresh medium containing chloramphenicol (red columns). Percentages of cells containing regrowth-delay bodies for more than 3 h (pink columns) were calculated from Fig. 3b. d Re-division Tid (the average initial doubling time) values of wild-type cells that were pre-cultured to the indicated time points. The Tid values were calculated based on the increase in cell numbers within the first 30 min of re-culturing (after diluting 40-fold) in fresh medium at 37 °C (for details, see Methods). e Survival rates of the indicated re-cultured stationary-phase wild-type cells that were treated with ofloxacin (5 μg/ml) or ampicillin (200 μg/ml) for 2 h (in fresh LB medium at 37 °C). The survival rates were calculated according to the equation: [colony-forming units (CFU) of the antibiotic-treated cells]/[colony-forming units of the untreated cells] ×100. f Live-cell fluorescence microscopic images merged with bright field of the re-cultured late stationary-phase ftsZ-mNeonGreen cells in the fresh ampicillin-containing LB medium (at 37 °C), as obtained at the indicated time points. Representative cells that exited (eventually became lysed) or maintained (unaltered) the regrowth lag is indicated by the white or red arrows, respectively. Scale bars, 3 μm. The symbol * in d and e denotes a significant difference between the compared pair of samples (P-value < 0.05, t-test). At least three biological replicates were analyzed in obtaining each value
