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Jaswal, K.

Publications and source records attributed to Jaswal, K..

3 recordsLinked to original sources
bioRxiv2024

Amino acid competition shapes Acinetobacter baumannii gut carriage

Antimicrobial resistance is an urgent threat to human health. Asymptomatic colonization is often critical for persistence of antimicrobial-resistant pathogens. Gut colonization by the antimicrobial-resistant priority pathogen Acinetobacter baumannii is associated with increased risk of clinical infection. Ecological factors shaping A. baumannii gut colonization remain unclear. Here we show that A. baumannii and other pathogenic Acinetobacter evolved to utilize the amino acid ornithine, a non- preferred carbon source. A. baumannii utilizes ornithine to compete with the resident microbiota and persist in the gut in mice. Supplemental dietary ornithine promotes long-term fecal shedding of A. baumannii. By contrast, supplementation of a preferred carbon source--monosodium glutamate (MSG)-- abolishes the requirement for A. baumannii ornithine catabolism. Additionally, we report evidence for diet promoting A. baumannii gut carriage in humans. Together, these results highlight that evolution of ornithine catabolism allows A. baumannii to compete with the microbiota in the gut, a reservoir for pathogen spread.

microbiology↗
bioRxiv2024

Commensal Yeast Promotes Salmonella Typhimurium Virulence

Enteric pathogens engage in complex interactions with the host and the resident microbiota to establish gut colonization. Although mechanistic interactions between enteric pathogens and bacterial commensals have been extensively studied, whether and how commensal fungi affect pathogenesis of enteric infections remains largely unknown. Here we show that colonization with the common human gut commensal fungus Candida albicans worsened infections with the enteric pathogen Salmonella enterica serovar Typhimurium. Presence of C. albicans in the mouse gut increased Salmonella cecum colonization and systemic dissemination. We investigated the underlying mechanism and found that Salmonella binds to C. albicans via Type 1 fimbriae and uses its Type 3 Secretion System (T3SS) to deliver effector proteins into C. albicans. A specific effector, SopB, was sufficient to manipulate C. albicans metabolism, triggering increased arginine biosynthesis in C. albicans and the release of millimolar amounts of arginine into the extracellular environment. The released arginine, in turn, induced T3SS expression in Salmonella, increasing its invasion of epithelial cells. C. albicans deficient in arginine production was unable to increase Salmonella virulence in vitro or in vivo. In addition to modulating pathogen invasion, arginine also directly influenced the host response to infection. Arginine-producing C. albicans dampened the inflammatory response during Salmonella infection, whereas C. albicans deficient in arginine production did not. Arginine supplementation in the absence of C. albicans increased the systemic spread of Salmonella and decreased the inflammatory response, phenocopying the presence of C. albicans. In summary, we identified C. albicans colonization as a susceptibility factor for disseminated Salmonella infection, and arginine as a central metabolite in the cross-kingdom interaction between fungi, bacteria, and host.

microbiology↗
bioRxiv2020

Metabolism of long-chain fatty acids affects disulfide bond formation in Escherichia coli and activates envelope stress response pathways as a combat strategy

The envelope of gram-negative bacteria serves as the first line of defense against environmental insults. Therefore, its integrity is continuously monitored and maintained by several envelope stress response (ESR) systems. Due to its oxidizing environment, the envelope represents an important site for disulfide bond formation. In Escherichia coli, the periplasmic oxidoreductase, DsbA introduces disulfide bonds in substrate proteins and transfers electrons to the inner membrane oxidoreductase, DsbB. Under aerobic conditions, the reduced form of DsbB is re-oxidized by ubiquinone, an electron carrier in the electron transport chain (ETC). Given the critical role of ubiquinone in transferring electrons derived from the oxidation of reduced cofactors, we were intrigued whether metabolic conditions that generate a large number of reduced cofactors render ubiquinone unavailable for disulfide bond formation. To test this, here we investigated the influence of metabolism of long-chain fatty acid (LCFA), an energy-rich carbon source, on the redox state of the envelope. We show that LCFA degradation increases electron flow in the ETC. Further, we find that whereas cells metabolizing LCFAs exhibit several characteristics of insufficient disulfide bond formation, these hallmarks are averted in cells exogenously provided with ubiquinone. Importantly, the ESR pathways, Cpx and {sigma}E, are activated by envelope signals generated during LCFA metabolism, and these systems maintain proper disulfide bond formation. We find that {sigma}E downregulation hampers disulfide bond formation only in the absence of Cpx, and amongst the two ESR systems, only Cpx senses redox-dependent signal and is induced to a greater extent by LCFAs. Therefore, we argue that Cpx is the primary ESR that senses and maintains envelope redox homeostasis. Taken together, our results demonstrate an intricate relationship between cellular metabolism and disulfide bond formation dictated by ETC and ESR, and provide the basis for examining whether similar mechanisms control envelope redox status in other gram-negative bacteria. Author summaryDisulfide bonds contribute to the folding and stability of many extracytoplasmic proteins in all domains of life. In gram-negative bacteria, including Escherichia coli, disulfide bond formation occurs in the oxidizing environment of the periplasmic space enclosed within the outer and inner membrane layers of the envelope. Because disulfide-bonded proteins are involved in diverse biological processes, bacteria must monitor the envelope redox status and elicit an appropriate response when perturbations occur; however, these mechanisms are not well elucidated. Here, we demonstrated that the metabolism of an energy-rich carbon source, long-chain fatty acid (LCFA) hampers disulfide bond formation in E. coli. An envelope stress response (ESR) system, Cpx, senses this redox imbalance and maintains proper disulfide bond formation. The {sigma}E pathway, another ESR system, plays an ancillary role in maintaining redox homeostasis. LCFA metabolism, disulfide bond formation, and ESR systems have independently been implicated in the pathogenesis of several gram-negative bacteria. The present study sets the basis to explore whether LCFA metabolism impacts the virulence of these bacteria by influencing the redox status of their envelope and activation of ESR pathways.

microbiology↗