Bactericidal activity of endogenous MceA in the absence of all the other proteins encoded by the MccE492 gene cluster. (A and B) Serial dilutions of overnight cultures of DB503 (rpoA+) with pBAD101 (vector), pAB12 (Δss-MceA), or pAB11 (PhoA73-MceA) and of DB512 (rpoA341) with pBAD101 (vector), pAB12 (Δss-MceA), or pAB11 (PhoA73-MceA) were spotted (5 μl) on LB plates without arabinose (A) or with 0.2% arabinose (B) and incubated overnight at 37°C. Results shown here are representative of three independent experiments. (C) Viability assay of cultures of DB503 (rpoA+) with pBAD101 (vector), pAB12 (Δss-MceA), or pAB11 (PhoA73-MceA) and of DB512 (rpoA341) with pBAD101 (vector), pAB12 (Δss-MceA), or pAB11 (PhoA73-MceA) after 1 h of arabinose (0.2%) induction. Each value represents the average of three independent cultures. Error bars indicate standard deviations. (D) Synthesis levels of Δss-MceA and PhoA73-MceA. Cultures of AB3 (MccE492-resistant strain; see below) with pBAD101 (vector), pAB12 (Δss-MceA), or pAB11 (PhoA73-MceA) were pulse-labeled as described in Materials and Methods. Proteins were immunoprecipitated with anti-MceA antiserum (lower panel) or with anti-OmpA antiserum (upper panel) and detected by SDS-PAGE and autoradiography.