Fig 4.

Awakening kinetics of dormant E. coli. (A) After antibiotic challenge, individual surviving cells of E. coli do not initiate growth simultaneously but start growing at different time points spread throughout 2 weeks of incubation. Gradual awakening is apparent in single-cell experiments employing microtiter plates and in conventionally plated petri dishes. Recovery at the end of 2 weeks is designated total recovery and is assigned a value of 100%; earlier data points are presented as fractions of this value, with standard deviations indicated. The results represent data from three independent experiments, two of which employed gentamicin and one ofloxacin, all showing similar kinetics of growth initiation. (B) In a single growth experiment involving cells remaining after gentamicin treatment, we extended the incubation period to 2 months and continued to observe new growth. Note a much lower level of cell recovery in petri dishes versus single-cell experiments in microtiter plates. Note also that gradual awakening is not apparent in petri dishes, likely due to overgrowth by colonies developing early in incubation. Incidentally, this may be one reason why the phenomenon was not observed in earlier studies.