Fig 2. The two-component response regulator BfmR is required for desiccation tolerance.

A. baumannii strains were grown overnight in LB medium, and then cells were washed with water, dried, and assessed for desiccation tolerance at 25°C and 80% RH. (A) The survival of dried cells from the wild-type strain ATCC 17961 and derivatives isolated after extended culture in LB medium were tested. Samples from the initial inoculum and after 7 days of drying were diluted and spotted onto the surface of an LB plate. These data are representative of at least two independent experiments. (B) A representation of the BfmR protein showing the relative positions of the receiver domain (REC domain, gray box), the DNA-binding helix-turn-helix domain (HTH domain, hashed box), and the nucleotide and corresponding amino acid substitutions identified in the strains tested in panel (A). (C) A. baumannii strains ATCC 17961 (solid triangle), 17961-ΔbfmR (solid circle), 17961-ΔbfmR carrying vector plasmid pWH1266 (X), and 17961-ΔbfmR carrying an intact copy of bfmR on plasmid pJF-bfmR (open circle) were assessed for drying survival on the indicated days. The data presented are the mean ± SD from at least four independent experiments. (D) Cells from strains ATCC 17961, 17961-bfmR-254C>T, and 17961-bfmR-689T>C carrying either no plasmid (–), vector plasmid pWH1266 (v), or plasmid pJF-bfmR for complementation (c) were tested for survival after drying. Samples from the initial inoculum and after 7 days of drying were diluted and spotted onto the surface of an LB plate. These data are representative of at least two independent experiments.