New insights in the role of HtdA in the regulation of R27 conjugation

► HtdA is involved in the transcriptional repression of four R27 plasmid tra operons. ► HtdA does not exert its effect as a classical repressor. ► The HtdA mediated regulatory pathway involves other R27 encoded factors. ► The HtdA mediated regulation of conjugation is independent of the R27 H-NS protein.