A Nitrogen Metabolic Enzyme Provides Salmonella Fitness Advantage by Promoting Utilization of Microbiota-Derived Carbon Source

Abstract

Microbes support their growth in vertebrate hosts by exploiting a large variety of dietary components as nutrients, which determines the composition of gut microbiota. A pathogen Salmonella expands by utilizing 1,2-propanediol, a microbiotafermented product, during mucosal inflammation. However, it remains largely unknown how the pathogen decides which nutrient to consume from the complex mixture in the gut. Here, we show that Salmonella enterica serovar Typhimurium utilizes 1,2-propanediol by EIIA Ntr (a nitrogen-metabolic PTS component implicated in virulence)-mediated regulation of the pdu operon, thereby expanding in the murine intestine. Propionyl-CoA, a metabolic intermediate produced by 1,2-propanediol catabolism, elevates EIIA Ntr protein amounts, entailing positive feedback, thereby boosting the 1,2-propanediol-utilization process. EIIA Ntr promotes pdu expression by enhancing glutathione synthesis. CRP (cAMP receptor protein) induces pdu genes by increasing EIIA Ntr expression in response to glucose availability. Notably, EIIA Ntr -mediated 1,2-propanediol-utilization conferred a growth benefit even under high glucose conditions which reduces CRP activity. The EIIA Ntrmediated activation is likely conserved in pathogenic enterobacteria including Escherichia coli. Collectively, our findings suggest that Salmonella promotes its fitness by precisely modulating the utilization system for microbiota-derived carbon source. They also suggest that Salmonella may integrate signals, processed via EIIA Ntr , into its metabolic program as well as virulence circuit. KEYWORDS: nitrogen-metabolic phosphotransferase system (PTS Ntr ), EIIA Ntr , cAMP receptor protein (CRP), 1,2-propanediol catabolism, pdu operon Special Issue: Gut Pathogens

The role of nitrogen-responsive regulators in controlling inorganic polyphosphate synthesis in Escherichia coli

“…The nitrogen phosphotransferase system (PTS Ntr ) is a regulatory cascade that responds to nitrogen limitation and regulates the activity of multiple proteins in Enterobacteriacea (Fig. 4a) [42,[85][86][87][88][89]. The genes encoding PtsN (also known as EIIA Ntr ) and NPr, homologues of the EIIA and HPr proteins of the well-characterized carbon PTS [90], are encoded in the rpoN operon (Fig.…”

“…PtsP (also known as EI Ntr ), which is homologous to EI of the carbon PTS [38,90], responds to both glutamine and α-ketoglutarate as signals of cellular nitrogen limitation by autophosphorylation [69,91], ultimately resulting in phosphorylation of NPr and PtsN [92]. Both NPr and PtsN interact with and regulate the activity of a variety of proteins, typically depending on their phosphorylation states [42,[85][86][87][88][89].…”

“…These results argue against a role for PtsN abundance in polyP regulation in E. coli. PtsN regulates other proteins by direct physical interaction [42,[85][86][87][88][89], so we used a bacterial two-hybrid assay [57] to test whether PtsN interacts with PPK in vivo, and found no evidence for such an interaction (Fig. 5e).…”

The nitrogen phosphotransferase regulator PtsN (EIIANtr) regulates inorganic polyphosphate production inEscherichia coli

“…PtsP (also known as EI Ntr ), which is homologous to EI of the carbon PTS (34,68), responds to both glutamine and a-ketoglutarate as signals of cellular nitrogen limitation by autophosphorylation (37,69), ultimately resulting in phosphorylation of NPr and PtsN (70). Both NPr and PtsN interact with and regulate the activity of a variety of proteins, typically depending on their phosphorylation states (62)(63)(64)(65)(66)(67). Based on these facts and our results showing roles for PhoP and GlmS in polyP regulation we hypothesized that the PTS NTr might form part of the link between nitrogen limitation and polyP synthesis.…”

“…Both abundance and phosphorylation of PtsN are therefore potential variables in any PtsN-dependent regulatory system. PtsN abundance in Salmonella is also regulated in response to carbon source availability (63). We constructed strains encoding chromosomal fusions of the 3xFLAG epitope tag to the Cterminus of PtsN (62) to allow us to determine whether our polyP-inducing stress conditions led to changes in PtsN abundance in E. coli.…”