Phage resistance of YB3558 and YB3559. Resistance to the Caulobacter phage ΦCbK was assayed as described in the Methods. Dilutions of cells were mixed with phage stock and spotted onto PYE plates. CB15 is sensitive to the phage, ΔpodJ is resistant, and YB3558 shows virtually the same phage resistance as ΔpodJ. Complementation with ctrA under native control (YB3559) decreases phage resistance to nearly wild-type levels.