Figure 2. Increased extracellular DNA and lysis occur in biofilm-enhanced cultures.

A) Cell-free supernatants contain more DNA under biofilm-enhancing conditions. Supernatants were isolated from cultures (at a similar OD₆₀₀) of WT, ΔcprS, ΔflhA, or ΔcprS ΔflhA grown in either MH alone or MH/DOC. Equal volumes were used as templates for qPCR. DNA amounts are normalized to WT in MH alone. Error bars represent the mean of three separate cultures. *p<0.0001; **p = 0.0015; NS p = 0.42, unpaired t-test. B) Lysis, independent of flagella, occurs under conditions that promote biofilms. Cell-free supernatants were isolated as in above. Both total cellular protein (‘Bacteria’) and supernatants (‘Media’) were analyzed by Western blotting with an antibody specific for the cytoplasmic response regulator CosR.