Biology subjects

Nguyen, B. D.

Publications and source records attributed to Nguyen, B. D..

4 recordsLinked to original sources

bioRxiv2024

Interplay between chemotaxis, quorum sensing, and metabolism regulates Escherichia coli-Salmonella Typhimurium interactions in vivo

Motile bacteria use chemotaxis to navigate complex environments like the mammalian gut. These bacteria sense a range of chemoeffector molecules, which can either be of nutritional value or provide a cue for the niche best suited for their survival and growth. One such cue molecule is the intra- and interspecies quorum sensing signaling molecule, autoinducer-2 (AI-2). Apart from controlling collective behavior of Escherichia coli, chemotaxis towards AI-2 contributes to its ability to colonize the murine gut. However, the impact of AI-2-dependent niche occupation by E. coli on interspecies interactions in vivo is not fully understood. Here, using the C57BL/6J mouse infection model, we show that chemotaxis towards AI-2 contributes to nutrient competition and thereby affects colonization resistance conferred by E. coli against the enteric pathogen Salmonella enterica serovar Typhimurium (S. Tm). Like E. coli, S. Tm also relies on chemotaxis, albeit not towards AI-2, to compete against residing E. coli in a gut inflammation-dependent manner. Finally, by using a barcoded mutant library pool of S. Tm, we analyzed how AI-2 signaling in E. coli affects the central metabolism of S. Tm. AI-2-dependent niche colonization by E. coli specifically affected the fitness of S. Tm mutants deficient in fumarate respiration ({Delta}dcuABC) or mannose ({Delta}manA) utilization. Our findings thus provide important insights into AI-2-mediated E. coli-S. Tm interactions during gut infection. Author SummaryBoth chemotaxis and AI-2 quorum sensing systems have been extensively studied in Escherichia coli. Despite our understanding of these systems at a molecular level in vitro, their physiological relevance in vivo, particularly in the context of mammalian gut colonization, remains less explored. Building on our previous work on the role of chemotaxis and AI-2 signaling in E. coli gut colonization, we investigated their roles in interspecies interactions. Specifically, we examined how AI-2-dependent colonization by E. coli affects its competition with the enteric pathogen Salmonella enterica serovar Typhimurium (S. Tm) and the metabolic requirements for S. Tm growth. Our data show that AI-2 signaling contributes to colonization resistance of E. coli against S. Tm. Although S. Tm also requires chemotaxis to grow efficiently in E. coli-colonized mice, this is independent of its ability to sense AI-2. Notably, AI-2-dependent niche occupation by E. coli altered S. Tm metabolism at different stages of infection. Collectively, our findings highlight how AI-2 signaling in one species can affect the metabolism of its interaction partners in vivo.

microbiology↗

bioRxiv2024

Monosaccharides Drive Salmonella Gut Colonization in a Context-Dependent Manner

The carbohydrates that fuel gut colonization by S. Typhimurium are not fully known. To investigate this, we designed a quality-controlled mutant pool to probe the metabolic capabilities of this enteric pathogen. Using WISH-barcoding, we tested 35 metabolic mutants across five different mouse models, allowing us to differentiate between context-dependent and context-independent nutrient sources. Results showed that S. Typhimurium uses D-glucose, D-mannose, D-fructose, and D-galactose as context-independent carbohydrates across all models. The utilization of N-acetylglucosamine and hexuronates, on the other hand, was context-dependent. Furthermore, we showed that D-fructose is important in strain-to-strain competition between Salmonella serovars. Complementary experiments confirmed that D-glucose, D-fructose, and D-galactose are excellent niches for S. Typhimurium to exploit during colonization. Quantitative measurements revealed sufficient amounts of D-glucose and D-galactose in the murine cecum to drive S. Typhimurium colonization. Understanding these key substrates and their context-dependent use by enteric pathogens will inform the future design of probiotics and therapeutics to prevent diarrheal infections such as non-typhoidal salmonellosis.

microbiology↗

bioRxiv2023

mBARq: a versatile and user-friendly framework for the analysis of DNA barcodes from transposon insertion libraries, knockout mutants and isogenic strain populations

DNA barcoding has become a powerful tool for assessing the fitness of strains in a variety of studies, including random transposon mutagenesis screens, attenuation of site-directed mutants, and population dynamics of isogenic strain pools. However, the statistical analysis, visualization and contextualization of the data resulting from such experiments can be complex and require bioinformatic skills. Here, we developed mBARq, a user-friendly tool designed to simplify these steps for diverse experimental setups. The tool is seamlessly integrated with an intuitive web app for interactive data exploration via the STRING and KEGG databases to accelerate scientific discovery.

bioinformatics↗

bioRxiv2023

Intraluminal neutrophils limit epithelium damage by reducing pathogen assault on intestinal epithelial cells during Salmonella gut infection

Recruitment of neutrophils into the gut epithelium is a cardinal feature of intestinal inflammation in response to enteric infections. Previous work using the model pathogen Salmonella Typhimurium (S. Tm) established that invasion of intestinal epithelial cells by S.Tm leads to recruitment of neutrophils into the gut lumen, where they can reduce pathogen loads transiently. Notably, a fraction of the pathogen population can survive this defense, re-grow to high density, and continue triggering enteropathy. However, the functions of intraluminal neutrophils in the defense against enteric pathogens and their effects on preventing or aggravating epithelial damage are still not fully understood. Here, we address this question via neutrophil depletion in different mouse models of Salmonella colitis, which differ in their degree of enteropathy. In an antibiotic pre-treated mouse model, neutrophil depletion by an anti-Ly6G antibody exacerbated epithelial damage. This could be linked to compromised neutrophil-mediated elimination and reduced physical blocking of the gut-luminal S.Tm population such that the pathogen density remained high near the epithelial surface throughout the infection. The removal of luminal S. Tm by gentamicin, an antibiotic restricted to the gut lumen, reversed the effect of neutrophil depletion on epithelial cell loss. Strikingly, when using germ-free mice and an S. Tm ssaV mutant capable of epithelium invasion, but attenuated for survival and growth within host tissues, neutrophil depletion caused exacerbated immune activation of the gut mucosa and a complete destruction of the epithelial barrier. Together, our data indicate that intraluminal neutrophils are central for maintaining epithelial barrier integrity during acute Salmonella-induced gut inflammation, by limiting the sustained pathogen assault on the epithelium in a critical window of the infection. Highlights{circ} After the first wave of mucosal invasion (day 1 p.i.), S. Tm maintains the assault from the lumen, triggering the continued expulsion of epithelial cells in antibiotic pre-treated mice. {circ}Neutrophil recruitment into the gut lumen is essential to limit this continued Salmonella attack on the epithelium. {circ}In antibiotic pre-treated SPF mice, neutrophil depletion exacerbates S. Tm invasion, causing excessive epithelial cell loss, which compromises epithelial barrier integrity at later time points (day 2-3 p.i.). {circ}In germ-free mice, neutrophil depletion exacerbates epithelial responses and epithelial barrier destruction even more strongly than in streptomycin pre-treated SPF mice. {circ}Gentamicin treatment and ssaV mutant infections indicate that neutrophils prevent epithelial damage by eliminating and physically blocking gut-luminal pathogens.

immunology↗