Fig. 1

BfmR is required for A. baumannii pellicle formation and secretion of Hcp into culture media. a and b Pellicles formed by A. baumannii V15 (WT), ΔbfmRS mutant, and ΔbfmRS strain complemented with the plasmids pbfmRS or pbfmR: Macroscopic images of formed pellicles (a); Quantitative evaluation of pellicles with values normalized by the total growth volume (b). c and d 12.5% SDS-PAGE gel view of TCA-precipitated total protein fraction from culture media of WT, ΔbfmRS, and ΔbfmRS complemented with the plasmids pbfmRS or pbfmR (c); and WT, Δhcp mutant, and Δhcp complemented with a plasmid phcp (d). Proteins were precipitated with TCA, separated by 12.5% SDS-PAGE, and visualized by staining with Coomassie blue. Numbers on the left denote molecular mass in kDa. e and f Expression levels of A. baumannii V15 transcripts hcp (e) and tssM (f) in WT, ΔbfmRS, and ΔbfmRS mutant complemented with pbfmR. Expression data in the graphs are displayed as a fold change compared to the WT which is set at 1. hcp gene in plasmid phcp was induced using IPTG concentration of 0.1 mM. Error bars represent standard deviation. **, p < 0.01; ***, p < 0.001, relative to WT.