FIG 4.

Cell division profile of persister cells indicates survival of nondividing cells. Cells were grown to stationary phase in LB medium and diluted in 50% HIS (A and B) or 50% serum (C and D). Cells were incubated without antibiotics (no AB) and in the presence of ampicillin (Amp; 200 μg/ml), norfloxacin (Nor; 5 μg/ml), or amikacin (Ami; 25 μg/ml).The distributions of the fluorescence levels of events (single cells) analyzed by flow cytometry are presented as histograms consisting of 376 repartition bins. The numbers of events with the respective GFP fluorescence levels in 1-ml cell cultures from HIS (A) or serum (C) are shown. Differently colored histograms represent conditions as follows: filled gray, without antibiotics; yellow, ampicillin; green, norfloxacin; and dashed red, amikacin. The norfloxacin and amikacin lines mostly overlap. (B and D) After 150 min, the CFU were determined by plating, and the number GFP-positive events was measured by flow cytometry (FACS events).