B. thailandensis-encoded emrB-bif R operon. (A) The emrB-bif R operon (BTH_I0541–0542/BTH_RS14955–14960) is oriented divergently to a gene annotated as ecsC (BTH_I0540/BTH_RS14950). Two imperfect palindromes in the intergenic region are shown bold and underlined. Blue lines beneath the arrows depicting open reading frames represent the positions of PCR amplicons used for qRT-PCR. Inverted triangles indicate positions of transposon insertion. (B) Verification of emrB-bif R operon by PCR amplification of emrB fragment. Lane 1, negative control using RNA as template; lane 2, positive control using genomic DNA as template; lane 3, cDNA synthesized using bif R-specific primer as template. (C) Growth curve of wild-type, emrBΔ-bif RΔ and the corresponding mutant strains complemented with emrB (e) or emrB-bif R (e-b). (D) Growth curve of wild-type, bif RΔ, and the corresponding complemented strains; growth curves are representative of triplicate cultures. The doubling time for WT was ∼25 min, compared to ∼20 min for emrBΔ-bif RΔ and ∼55 min for bif RΔ.