Fig 4. Activation of the yjiY promoter in various γ-proteobacterial species growing in LB medium.

Previous studies reported transient BtsS/BtsR-mediated yjiY promoter activation in E. coli grown in LB medium shortly before cells enter stationary phase [9]. Each species was transformed with an E. coli yjiY-lux reporter plasmid, and luminescence levels (blue) as well as growth (black dotted line) were measured over time. Escherichia coli (Ec), Citrobacter freundii (Cf), Salmonella enterica (Se), Enterobacter aerogenes (Ea), Xenorhabdus szentirmaii (Xs), Serratia marcescens (Sm), Yersinia enterocolitica (Ye), Vibrio harveyi (Vh) and Aeromonas hydrophila (Ah). Degrees of divergence of the BtsS-type proteins of the selected species (based on phylogenetic tree in Fig 2A) to the E. coli BtsS are indicated above the graphs (in black—members of the Enterobacteriaceae, in grey—members of other γ-proteobacterial families).