RegA, the Regulator of the Two-Component System RegB/RegA of Brucella suis, Is a Controller of Both Oxidative Respiration and Denitrification Required for Chronic Infection in Mice

Abstract

Adaptation to oxygen deficiency is essential for virulence and persistence of Brucella inside the host. The flexibility of this bacterium with respect to oxygen depletion is remarkable, since Brucella suis can use an oxygen-dependent transcriptional regulator of the FnrN family, two high-oxygen-affinity terminal oxidases, and a complete denitrification pathway to resist various conditions of oxygen deficiency. Moreover, our previous results suggested that oxidative respiration and denitrification can be simultaneously used by B. suis under microaerobiosis. The requirement of a functional cytochrome bd ubiquinol oxidase for nitrite reductase expression evidenced the linkage of these two pathways, and the central role of the two-component system RegB/RegA in the coordinated control of both respiratory systems was demonstrated. We propose a scheme for global regulation of B. suis respiratory pathways by the transcriptional regulator RegA, which postulates a role for the cytochrome bd ubiquinol oxidase in redox signal transmission to the histidine sensor kinase RegB. More importantly, RegA was found to be essential for B. suis persistence in vivo within oxygen-limited target organs. It is conceivable that RegA acts as a controller of numerous systems involved in the establishment of the persistent state, characteristic of chronic infections by Brucella.

RegA Plays a Key Role in Oxygen-Dependent Establishment of Persistence and in Isocitrate Lyase Activity, a Critical Determinant of In vivo Brucella suis Pathogenicity

“…The oxygen-dependent regulator fnrN (BR0654), cydD (BRA0508) and cydC (BRA0509) (Table S1) of the cyd operon encoding the bd ubiquinol oxidase of high affinity for oxygen were very strongly induced by RegA, as shown previously (Abdou et al, 2013). One and five potential RegA-binding sites were accurately detected in cydD and fnrN upstream sequences, respectively (Table S3).…”

“…Expression of RegA-dependent genes specifically induced under microaerobiosis or anaerobiosis ( fnrN, ccoN , and nirK ) (Abdou et al, 2013) or participating in nucleic acids metabolism ( ada and rpoZ ) was therefore quantified during the first 4 days. Accordingly, the whole-genome microarray analysis was performed with three independent wild-type and Δ regA cultures harvested at day 3, when anaerobic conditions become established but the viability of both strains was still rather similar.…”

“…Purified RNAs were controlled quantitatively and qualitatively, and for absence of contaminating DNA in 0.5 μg samples as previously described (Abdou et al, 2013). …”

Toll-Like Receptors 2 and 4 Cooperate in the Control of the Emerging Pathogen Brucella microti

“…like B. melitensis, B. abortus or B. suis or with the new ones B. ceti and B. pinnipedialis leads to a typical replication pattern in the spleen and liver, characterized by a multiplication phase until the number of bacteria reaches its maximum (acute phase), followed by a chronic plateau phase and a declining phase that ends by the clearing of the bacteria in both organs. The duration of these phases depends on the route and the dose of the inoculum and the chronic phase can last more than 20 weeks (Montaraz and Winter, 1986; Edmonds et al, 2002; Abdou et al, 2013; Nymo et al, 2016). None of the classical Brucella spp.…”

Genomic analysis of the original Elberg Brucella melitensis Rev.1 vaccine strain reveals insights into virulence attenuation

“…The AraC-like transcriptional regulator DhbR was shown to regulate the biosynthesis of 2,3-DHBA and brucebactin, which play an important role in the virulence of B. abortus in its natural ruminant host [38]. RegA, the regulator of the RegB/RegA two-component system of B. suis , was shown to control oxidative respiration and denitrification, which enables Brucella to adapt to oxygen-limited conditions, produce sufficient energy under low oxygen conditions, and eliminate toxic NO produced by macrophages [39]. Thus, the regulatory capabilities of Rev.1 appear to be reduced, which may contribute to the attenuation of this strain.…”