FIG 4.

Meropenem-induced spheroplasts can recover to form an exponentially growing population. A time-lapse montage of spheroplasts imaged upon removal of meropenem after 6 h of treatment is shown. The antibiotic was removed by addition of purified NDM-1 carbapenemase, followed by time-lapse microscopy on BHI⁺ agarose pads (0.8% [wt/vol] agarose). Images were then acquired 5 min apart for another 2 h. Both E. coli isolates were omitted since no spheroplasts were observed after 6 h of meropenem treatment. Scale bars, 5 μm.