AUTHOR=Tartilán-Choya Beatriz , Tejedor Carmen , Conde-Álvarez Raquel , Muñoz Pilar María , Vizcaíno Nieves 

TITLE=Characterization of three predicted zinc exporters in Brucella ovis identifies ZntR-ZntA as a powerful zinc and cadmium efflux system not required for virulence and unveils pathogenic Brucellae heterogeneity in zinc homeostasis

JOURNAL=Frontiers in Veterinary Science

VOLUME=10

YEAR=2024

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2023.1323500

DOI=10.3389/fvets.2023.1323500

ISSN=2297-1769

ABSTRACT=<p><italic>Brucella ovis</italic> causes non-zoonotic ovine brucellosis of worldwide distribution and is responsible for important economic losses mainly derived from male genital lesions and reproductive fails. Studies about the virulence mechanisms of this rough species (lacking lipopolysaccharide O-chains) are underrepresented when compared to the main zoonotic <italic>Brucella</italic> species that are smooth (with O-chains). Zinc intoxication constitutes a defense mechanism of the host against bacterial pathogens, which have developed efflux systems to counterbalance toxicity. In this study, we have characterized three potential <italic>B. ovis</italic> zinc exporters, including the ZntA ortholog previously studied in <italic>B. abortus</italic>. Despite an in-frame deletion removing 100 amino acids from <italic>B. ovis</italic> ZntA, the protein retained strong zinc efflux properties. Only indirect evidence suggested a higher exporter activity for <italic>B. abortus</italic> ZntA, which, together with differences in ZntR-mediated regulation of <italic>zntA</italic> expression between <italic>B. ovis</italic> and <italic>B. abortus</italic>, could contribute to explaining why the Δ<italic>zntR</italic> mutant of <italic>B. abortus</italic> is attenuated while that of <italic>B. ovis</italic> is virulent. Additionally, <italic>B. ovis</italic> ZntA was revealed as a powerful cadmium exporter contributing to cobalt, copper, and nickel detoxification, properties not previously described for the <italic>B. abortus</italic> ortholog. Deletion mutants for BOV_0501 and BOV_A1100, also identified as potential zinc exporters and pseudogenes in <italic>B. abortus</italic>, behaved as the <italic>B. ovis</italic> parental strain in all tests performed. However, their overexpression in the Δ<italic>zntA</italic> mutant allowed the detection of discrete zinc and cobalt efflux activity for BOV_0501 and BOV_A1100, respectively. Nevertheless, considering their low expression levels and the stronger activity of ZntA as a zinc and cobalt exporter, the biological role of BOV_0501 and BOV_A1100 is questionable. Results presented in this study evidence heterogeneity among pathogenic Brucellae regarding zinc export and, considering the virulence of <italic>B. ovis</italic> Δ<italic>zntA</italic>, suggest that host-mediated zinc intoxication is not a relevant mechanism to control <italic>B. ovis</italic> infection.</p>