The arginine/ornithine binding protein ArgT plays an essential role in <i>Brucella neotomae</i> / <i>Brucella melitensis</i> to prevent intracellular killing and contribute to chronic persistence in the host

<i>Brucella</i> species are facultative intracellular bacterial pathogens that cause the contagious zoonotic disease, brucellosis. <i>Brucella</i> spp. infect a wide range of animals, including livestock, wild animals, and marine mammals. Compared with other invasive bacterial pathogens, partial information is available on the virulence factors of <i>Brucella</i> that enable them to survive in the host. Here, we performed transposon-based random mutagenesis of <i>B. neotomae</i> and identified the arginine/ornithine binding protein, ArgT, as one of the crucial virulence determinants of <i>Brucella</i>. Deleting <i>ArgT</i> from <i>B. neotomae</i> or <i>B. melitensis</i> resulted in its attenuation in macrophages, which was restored upon complementation with an <i>ArgT</i> expression plasmid. We observed that macrophages infected with Δ<i>ArgT-B. neotomae</i> produced elevated levels of NO due to the inability of these mutants to deplete the host intracellular arginine through their importer. Furthermore, defective survival of Δ<i>ArgT B. neotomae</i> and <i>B. melitensis</i> was observed in the infected mice, which correlated with enhanced NO production in the mice. Our studies revealed that <i>ArgT</i> plays a vital role in preventing intracellular killing and contributes to the chronic persistence of <i>B. neotomae/B. melitensis</i> in the host. This study highlights the essential role of arginine in clearing intracellular infections and the subversion of this host defense mechanism by intracellular pathogens for their chronic persistence.