Due to its importance
in diverse energy metabolic processes, the ArcA regulon has been thoroughly characterized in E. coli [5, 12, 18]. Conversely, very little is known about the regulatory network controlled by ArcA in S. Typhimurium under anaerobic conditions. Although E. coli and S. Typhimurium share a very high genomic similarity (~75-80%) [19], we previously discovered that the Fnr (Fumarate Nitrate Reductase) regulon of S. Typhimurium is markedly different from the one identified in E. coli [20]. Due to the complementary roles of ArcA and Fnr in the regulation of cellular metabolism and adaptation to changes in redox, we hypothesized that the ArcA regulon of S. Typhimurium will also differ from that of E. coli. The results indicate that in S. Typhimurium, selleck kinase inhibitor as in E. coli, the ArcA regulon includes the core metabolic and energy
functions as well as motility. However, Salmonella-specific genes/operons regulated by ArcA include newly identified flagellar genes (mcpAC, cheV), Gifsy-1 prophage genes, a few SPI-3 genes (mgtBC, slsA, STM3784), and those for propanediol utilization. Furthermore, the arcA mutant was non-motile and was as virulent as the isogenic wild-type strain. We also identified 120 genes that were regulated by the anaerobic regulator, Fnr, as well as by ArcA. Methods Bacterial strains and growth conditions The bacterial strains used in this study are listed in Table 1. Wild-type (WT) S. Typhimurium this website (14028s) and its isogenic click here arcA mutant (NC 980) were used throughout. P22 phage
was used to move the arcA::Tn10 mutation from S. Typhimurium LT2 (TT17442) [21] to strain 14028 s. Transductants were plated on Evans Blue Uranine (EBU) agar and the arcA mutant was tested for its inability to grow on toluidine blue agar [22]. The Tn10 insertion junctions of the arcA mutant were confirmed by PCR and DNA sequencing. Additionally, the absence of the ArcA protein in the mutant was confirmed by Western blotting (Additional file 1: Figure S1 – lane 3). Table 1 List of strains, plasmids, and phage used in this study Strain, Plasmid, or Phage Relevant Characteristics Source and/or Reference Strains Salmonella Typhimurium 14028s Wild-type American Type Culture Collection TT17442/SL3052 (LT2) containing CRM1 inhibitor metE205 ara-9 cob-24::MudJ arcA201::Tn10d-Tet [21/S. Libby] NC980 14028 s containing arcA::Tn10 (Tetr) [TT17442 (P22) × 14028s] This study NC989 Same as NC980, but harboring parcA. This study Escherichia coli ER2420 Harboring pACYC177 New England Biolabs ER2925 ara-14 leuB6 fhuA31 lacY1 tsx78 glnV44 galK2 galT22 mcrA dcm-6 hisG4 rfbD1 R(zgb210::Tn10)TetS endA1 rpsL136 dam13::Tn9 xylA-5 mtl-1 thi-1 mcrB1 hsdR2 New England Biolabs Plasmids pACYC177 F- ara-14 leu fhuA2 Δ(gpt-proA)62 lacY1 glnV44 galK2 rpsL20 xyl-5 mtl-1 Δ(mcrC-mrr) HB101 New England Biolabs parcA An 897 base pair arcA amplicon from S.