Nature of the microgranular-fibrilar extracellular background in an E. coli strain susceptible to ampicillin, incubated with 32 μg/ml of the antibiotic. Control culture without ampicillin does not show the microgranular-fibrilar extracellular background (a), whereas it is evident in cultures treated with ampicillin (b). Incubation of the microgels with specific buffers for DNase I (c) or proteinase K (e) does not affect the background. The specific proteinase K buffer lyses the bacteria. The background disappears after incubation with DNase I (d), but not after proteinase K treatment (f).
Santiso et al. BMC Microbiology 2011 11:191 doi:10.1186/1471-2180-11-191