Interdependency on YmdB and RpoS for biofilm formation. (A) Effect of knocking out ymdB or rpoS on biofilm formation. Biofilm formation was measured in wild-type (ymdB + or rpoS+), KSK002 (∆ymdB) and rpoS mutant (Keio-∆rpoS) cells. (B) Dependency of RpoS and YmdB phenotype on biofilm formation. The effect of ectopic expression of RpoS or YmdB in the absence of ymdB or rpoS, respectively, on biofilm formation was determined. (C) Expression of RpoS and YmdB. Protein expression was detected by immunoblotting using antibodies against RpoS and 6xHistidine tagged YmdB (His-YmdB) as described in Methods. S1 protein level was used as a loading control. All biofilm formation data were obtained as described in Methods. Data represent the mean values from ten independent experiments.