ymcA knockout effects on the expression from the comK promoter are not bypassed by sof-1. (A and B) Luciferase assays for PcomK-luc expression were performed as described in Experimental procedures. (A) shows the effect of a ymcA knockout on PcomK-luc expression in a comK knockout. (B) shows the effect of ymcA and spo0F inactivation in a comK+ background, as well as the effects of sof-1. The strains used were as follows. (A) wild-type ΔcomK PcomK-luc (BD4893), ΔymcA ΔcomK PcomK-luc (BD7642). (B) wild-type PcomK-luc (BD4773), ΔymcA Δspo0F sof- 1 PcomK-luc (BD7608), ΔymcA PcomK-luc (BD7605), Δspo0F PcomK-luc (BD7606), Δspo0F sof-1 PcomK-luc (BD7607). The strains were all derivatives of IS75 and were grown in competence medium.