The regulon of Brucella abortus two-component system BvrR/BvrS reveals the coordination of metabolic pathways required for intracellular life

Abstract

Brucella abortus is a facultative intracellular pathogen causing a severe zoonotic disease worldwide. The two-component regulatory system (TCS) BvrR/BvrS of B. abortus is conserved in members of the Alphaproteobacteria class. It is related to the expression of genes required for host interaction and intracellular survival. Here we report that bvrR and bvrS are part of an operon composed of 16 genes encoding functions related to nitrogen metabolism, DNA repair and recombination, cell cycle arrest, and stress response. Synteny of this genomic region within close Alphaproteobacteria members suggests a conserved role in coordinating the expression of carbon and nitrogen metabolic pathways. In addition, we performed a ChIP-Seq analysis after exposure of bacteria to conditions that mimic the intracellular environment. Genes encoding enzymes at metabolic crossroads of the pentose phosphate shunt, gluconeogenesis, cell envelope homeostasis, nucleotide synthesis, cell division, and virulence are BvrR/BvrS direct targets. A 14 bp DNA BvrR binding motif was found and investigated in selected gene targets such as virB1, bvrR, pckA, omp25, and tamA. Understanding gene expression regulation is essential to elucidate how Brucella orchestrates a physiological response leading to a furtive pathogenic strategy.

Phenotypes controlled by the Brucella abortus two component system BvrR/BvrS are differentially impacted by BvrR phosphorylation

“…Overall, BvrRS influences the expression of more than 100 genes ( Viadas et al, 2010 ). Some of these genes encode enzymes at the metabolic crossroads of carbon and nitrogen pathways, reinforcing the role that BvrRS has in the coordination of gene expression, required for a successful B. abortus infection ( Rivas-Solano et al, 2022 ), a phenomenon also reflected in the proteome of the bvrR and bvrS mutants compared to wild-type Brucella ( Lamontagne et al, 2007 ).…”

“…Among those stands the two-component system (TCS) BvrR/BvrS (BvrRS) which has been consistently identified in independent unbiased approaches designed to understand the virulence mechanisms exerted by B. abortus ( López-Goñi et al, 2002 ; Viadas et al, 2010 ; Altamirano-Silva et al, 2018 ). BvrRS is part of an operon encompassing 16 genes, with orthologs in the phylogenetically related endosymbiont Sinorhizobium meliloti , and the plant pathogen Agrobacterium tumefaciens ( Rivas-Solano et al, 2022 ). It is composed of the sensor protein BvrS, which, upon activation, is auto-phosphorylated and then transfers the phosphate moiety to aspartate 58 of the response regulator, BvrR ( Altamirano-Silva et al, 2018 ).…”

“…It is composed of the sensor protein BvrS, which, upon activation, is auto-phosphorylated and then transfers the phosphate moiety to aspartate 58 of the response regulator, BvrR ( Altamirano-Silva et al, 2018 ). BvrR phosphorylation induces a conformational change that increases the protein’s affinity to promoter regions, impacting gene expression ( Sola-Landa et al, 1998 ; Altamirano-Silva et al, 2018 ; Rivas-Solano et al, 2022 ).…”

“…BvrRS activity also has a profound impact on membrane homeostasis. BvrRS exerts transcriptional control on membrane proteins such as Omp3a (Omp25) and Omp3b and enzymes related to LPS synthesis ( Guzman-Verri et al, 2002 ; Rivas-Solano et al, 2022 ). BvrRS-defective mutants show abnormal LPS acylation patterns and are susceptible to cationic peptides such as polymyxin B ( Manterola et al, 2005 , 2007 ).…”

“…BvrRS-defective mutants show abnormal LPS acylation patterns and are susceptible to cationic peptides such as polymyxin B ( Manterola et al, 2005 , 2007 ). Direct binding of phosphorylated BvrR to regulatory regions of tamA , pckA , omp25, virB1 and its own regulatory region has been shown ( Rivas-Solano et al, 2022 ). Overall, BvrRS influences the expression of more than 100 genes ( Viadas et al, 2010 ).…”