Regulon of SdiA in Salmonella Typhimurium and Typhi

SdiA is a LuxR-type protein found in some Enterobacteriaceae. SdiA encoding bacteria do not encode a luxI homolog and rely on foreign bacteria for the production of N-acyl homoserine lactones (AHLs), SdiA's ligand. The regulon of Salmonella SdiA is largely unknown. In this study, we measured the sdiA dependent transcriptional changes of two serovars of Salmonella, Typhimurium and Typhi, exposed to synthetic AHLs. This was evaluated in two experiments. First, the wild-type and sdiA mutant were grown in the presence of AHLs. In the second, sdiA mutants harboring an arabinose inducible copy of SdiA on a plasmid and vector control were grown with AHLs and arabinose. From this a putative regulon was established and confirmed with subsequent characterization experiments. Overall design: two pairs of two experiments are included in this study. The first pair was performed in Salmonella Typhimurium (wild-type 14028, sdiA mutant BA612). The second pair was performed in Salmonella Typhi (wild-type Ty2, sdiA mutant AMS001 and AMS002). In the first experiment, wild-type and sdiA mutant cultures were grown in LB broth in the presence of synthetic AHLs until late expontential phase. In the second experiment, sdiA mutant harboring either a plasmid copy of sdiA or vector control were grown in LB broth in the presence of synthetic AHLs and arabinose until late exponential phase. The plasmid copy of sdiA was placed in front of the araBAD promoter, which is induced by arabinose. Three biological replicates were collected per strain/condition