Regulation of Bacterial Conjugation in Microaerobiosis by Host-Encoded Functions ArcAB and SdhABCD

Abstract

The virulence plasmid of Salmonella enterica (pSLT) is an F-like conjugative plasmid that transfers efficiently in the mammalian gut, a microaerobic environment. This study identifies host-encoded activators and repressors of the pSLT transfer operon (tra). The transcription factor ArcA activates conjugation, particularly under microaerobic conditions, by binding upstream of the main tra promoter (p(traY)). Conversely, succinate dehydrogenase (SdhABCD) represses mating in aerobic conditions. ArcA's activation of the traY promoter is ArcB-independent in aerobiosis but requires ArcB in microaerobiosis. The absence of ArcA significantly reduces pSLT transfer, while the lack of Sdh increases it under aerobiosis. The ArcAB system enhances pSLT transfer in microaerobiosis by activating the tra operon and repressing the sdhCDAB operon.