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Microbiota-derived short-chain fatty acids modulate expression of Campylobacter jejuni determinants required for commensalism and virulence

ABSTRACT: Campylobacter jejuni effectively promotes commensalism in the intestinal tract of avian hosts and diarrheal disease in humans, yet components of intestinal environments sensed by the bacterium in either host to initiate interactions are mostly unknown. By analyzing a C. jejuni acetogenesis mutant that is defective in both converting acetyl-CoA to acetate and commensal colonization of young chicks, we discovered evidence for C. jejuni sensing spatial gradients of microbiota-derived short-chain fatty acids (SCFAs) and organic acids to modulate expression of determinants required for commensalism. We identified in C. jejuni an SCFA-influenced regulon composed by genes encoding catabolic enzymes and transport systems for amino acids C. jejuni requires for in vivo growth. Expression of these genes was reduced in the acetogenesis mutant, but restored upon supplementation with physiological concentrations of SCFAs such as acetate and butyrate that are present in the lower intestinal tract of avian and human hosts. Conversely, the organic acid lactate, which is abundant in the upper intestinal tract of these hosts where C. jejuni less efficiently colonizes reduced expression of this regulon. We propose a model whereby C. jejuni senses microbiota-produced SCFAs and lactate for spatial orientation in the avian and human host. Sensing these metabolites likely allows C. jejuni to locate preferred niches in the lower intestinal tract and induce expression of factors required for in vivo growth. Our findings provide insights into the types of signals C. jejuni monitors in the avian host for commensalism and likely in the human host to promote diarrheal disease.

ORGANISM(S): Campylobacter jejuni

PROVIDER: GSE86327 | GEO | 2016/09/02

SECONDARY ACCESSION(S): PRJNA341455

REPOSITORIES: GEO

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Project description:The symptoms of infectious diarrheal disease are mediated by the interplay between the host and pathogen. Campylobacter jejuni is the leading bacterial cause of diarrhea worldwide due to its near-ubiquitous zoonotic association with poultry. One of the outstanding questions is what factors drive the intestinal inflammation during the development of C. jejuni-mediated disease. Specifically, it is not known the extent to which the bacteria are responsible for the diarrheal symptoms via cell necrosis, or whether there is immune cell recruitment prior to tissue damage. To determine the stepwise process of inflammation that leads to diarrhea, we used a piglet ligated intestinal loop model to study the intestinal environment in response to C. jejuni. Pigs were chosen due to the anatomical similarity of the porcine intestine to the human intestine, as the basis of disease modeling is to understand the process of human disease. Using immunoassays and proteomic approaches, we found that neutrophils are most likely the predominant cell type recruited to the intestines of C. jejuni infected animals. In the lumen of the intestine, a number of neutrophil related proteins increased during C. jejuni infection, including proteins related to neutrophil migration (elastase and MMP9), actin reorganization and bacterial uptake (Cdc42, WAVE-2, and Arp2/3), and antimicrobial proteins (lipocalin-2, myeloperoxidase, S100A8, and S100A9). The appearance of neutrophils also corresponds with increases of both IL-8 and TNF-a. Compared to infection with the C. jejuni wild-type strain, infection with the noninvasive C. jejuni ∆ciaD mutant resulted in a blunted inflammatory response, with less inflammatory cytokines and neutrophil markers. These findings indicate that intestinal inflammation is driven by C. jejuni virulence, and that resident intestinal cells precipitate the inflammatory response. Using this new disease model, we have developed a platform to study the early immune events during C. jejuni infection.

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Microbiota-derived short-chain fatty acids modulate expression of Campylobacter jejuni determinants required for commensalism and virulence

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