DNA fragmentation in nucleoids from E. coli strain TG1 exposed to CIP in different culture times. The growth curve of the bacteria, evaluated by monitoring turbidity at OD600, is presented above. The distribution of the frequencies of the diffusion widths of DNA fragments from the nucleoids were categorized into the five classes 0 to IV described in Table 1 and Fig. 2. Aliquots from a batch culture were removed at 3 h (exponentially growing phase) and at 7, 9, and 23 h (stationary phase), incubated with 1 μg/ml CIP for 0 (i.e., technical processing time of 8 min) (medium) and 5 min (below), and then processed to determine the DNA fragmentation.