Metabolic flux analysis revealed key roles of ArcB in ADI pathway and IlvC in BCAA biosynthesis duringanaerobic growth and infection.

Abstract

Critical metabolic enzymes and pathways specific to bacterial adaptation in different host microenvironments directly contribute to bacterial pathogenicity. In this study, a virulent strain of the important zoonotic pathogenwas found to show enhanced growth under anaerobic conditions compared to aerobic conditions. Transcriptomic analysis found a significant suppression of many central metabolic genes during anaerobic growth of. The transcriptomic data were used to reconstruct a genome-scale metabolic network to assess the distribution of metabolic fluxes inunder different conditions. Significant activation of the arginine deiminase (ADI) and branched-chain amino acid (BCAA) biosynthesis pathways was identified. Gene deletion mutants ofandparticipating in these two pathways, respectively, were constructed. Compared to the wild-type strain, the Δmutant showed more significant growth deficiency under anaerobic conditions than under aerobic conditions. Accumulation of ATP and NH, the metabolites of the ADI pathway, was significantly higher whenwas cultured under anaerobic conditions, and this effect was attenuated in the Δmutant. The knockout of IlvC of the BCAA pathway disrupted the normal growth ofin valine- and isoleucine-limited medium under anaerobic conditions. Both Δand Δshowed attenuation in mice with decreased lethality, bacterial loads in tissues, and cytokine levels in serum, with the hypoxia-induced gene up-regulated in tissues. Therefore, ADI and BCAA pathways are critical forsurvival in response to hypoxia and infection, with ArcB and IlvC being promising drug targets.