FIG. 6.

(a) The purA mutant does not appear to be decorated with eDNA like the wild type. The presence of eDNA was determined electrophoretically by placing 20-μl portions of washed exponential-phase suspensions (optical density at 546 nm, 5.0) of wild-type and purA mutant populations in a 0.8% agarose gel, which was resolved by electrophoresis at 60 V for 60 min. The marker was HindIII-digested λ DNA. (b) Susceptibility of exponential-phase wild-type and purA mutant populations to actinomycin D determined with and without prior treatment with DNase. Mid-exponential-phase planktonic cultures were washed and treated either with 5 U/ml RNase-free DNase or with water for 30 min prior to exposure to 50 μg·ml⁻¹ actinomycin D.