Project description:LF82, an adherent invasive Escherichia coli (AIEC) pathobiont, is associated with Crohn’s disease, an inflammatory bowel disease of unknown etiology. No genetic features have been identified that distinguish AIEC strains, such as LF82, from “commensal” or pathogenic E. coli. We investigated an extremely rare single nucleotide polymorphism (SNP) within the highly conserved rpoD gene, encoding sigma70 [primary sigma factor, RNA polymerase (RNAP)]. We demonstrate that sigma70 D445V results in transcriptome and phenotypic changes consistent with LF82 phenotypes, including increased biofilm formation and antibiotic resistance. The position of D445V within RNAP is predicted to affect spacer interaction; in vitro transcriptions reveal that the variant increases transcription from several promoters with a 16 bp spacer and a -14G:C. Our work demonstrates that a single SNP within the bacterial primary sigma can lead to myriad gene expression changes/ new phenotypes and suggests an underrecognized mechanism by which pathobionts and other strain variants can emerge.
Project description:Imbalance in beneficial and harmful bacteria underlies gastrointestinal diseases, such as inflammatory bowel disease. Here, we demonstrated that certain E. coli strains, specifically adherent-invasive E. coli (AIEC), utilize a serine metabolism pathway to outcompete other E. coli strains in the inflamed gut. In contrast, amino acid metabolism has a minimal effect on their competitive fitness in the healthy gut. The availability of luminal serine used for the competition of E. coli is largely dependent on dietary intake, as the inflammation-induced blooms of AIEC are significantly blunted when amino acids, particularly serine, are removed from the diet. Thus, intestinal inflammation regulates the intraspecific competition between Enterobacteriaceae by eliciting their metabolic reprogramming.
Project description:Our aim was to identify candidate transcripts that distinguish AIEC from non-invasive E. coli (NIEC) strains and might be useful for rapid and accurate identification of AIEC by culture-independent technology. We performed comparative RNA-Sequence (RNASeq) analysis using AIEC strain LF82 and NIEC strain HS during exponential and stationary growth.
Project description:The complex reservoir of metabolite-producing bacteria in the gastrointestinal tract contributes tremendously to human health and disease. Bacterial composition, and by extension gut metabolomic composition, is undoubtably influenced by the use of modern antibiotics. Herein, we demonstrate that polymyxin B, a last resort antibiotic used for chronic multidrug resistant infections infections, influences the production of the genotoxic metabolite colibactin from adherent-invasive Escherichia coli (AIEC) NC101. Colibactin can augment colorectal cancer (CRC) through DNA double stranded breaks and interstrand crosslinks. While the structure and biosynthesis of colibactin has been elucidated, chemical-induced regulation of its biosynthetic gene cluster and subsequent production of the genotoxin by pathogenic E. coli are largely unexplored. This research highlights the regulation of the colibactin-producing biosynthetic gene cluster under polymyxin stress. Using a multi-omic approach, we have identified that polymyxin stress enhances the abundance of colibactin biosynthesis proteins (Clb’s) in multiple pks+ E. coli strains, including pro-carcinogenic AIEC: NC101, the probiotic strain: E. coli Nissle 1917, and the antibiotic testing strain: E. coli ATCC 25922. Expression analysis via qPCR revealed that increased transcription of clb genes likely contributes to elevated Clb protein levels in NC101. Enhanced production of Clb’s by NC101 under polymyxin stress matched an increased production of the colibactin prodrug motif, a proxy for the mature genotoxic metabolite. Furthermore, E. coli with heightened tolerance for polymyxin antibiotics induced greater DNA damage, assessed by quantification of γH2AX staining in cultured intestinal epithelial cells. This study establishes a key link between the polymyxin B stress response and colibactin production in pks+ E. coli. Ultimately, our findings will inform future studies investigating colibactin regulation, the microbial response to antibiotics in the gut, and the ability of seemingly innocuous commensal microbes to induce host disease.
Project description:The role of propionate-induced rearrangement of membrane proteins in the formation of the virulent phenotype of Crohn's Disease-associated adherent-invasive Escherichia coli. Adhesive-invasive Escherichia coli (AIEC) were first isolated from the ileal mucosa of a patient with Crohn's disease (CD) which is a severe chronic immune-mediated granulomatous inflammatory disease of the gastrointestinal tract. It turned out that they are able to successfully penetrate the mucin layer, overcome the epithelial barrier, and also survive and multiply inside macrophage. Bacteria with such properties were assigned to a special group of pathobiont adhesive-invasive E. coli. AIEC activity is accompanied by the release of pro-inflammatory cytokines, i.e. surviving and multiplying inside macrophages, they enhance the inflammatory process. The role of AIEC in the onset or chronicity of CD is not well-defined. However, it has been proposed that these bacteria could trigger the onset of the inflammatory process as a result of the invasion of intestinal epithelial cells, and then, due to their survival within macrophages, they could stimulate chronic inflammation and granuloma developmen. Pathogens use a variety of mechanisms, including the induction of inflammation, the direct or indirect destruction of commensal species, and the use of alternative carbon sources to survive. AIEC are shown to be able to utilize ethanolamine and propanediol, which are formed during the catabolism of phospholipids, fucose or rhamnose, propionate and other metabolites. Metabolic plasticity is thought to allow AIEC to act as an opportunistic pathogen in conditions of intestinal inflammation. We have previously shown that passage of AIEC from a CD patient (CD isolate) on M9 minimal medium supplemented with sodium propionate (PA) as a carbon source leads to a strong increase, and passage on M9 medium supplemented with glucose, on the contrary, leads to a significant decrease in adhesive-invasive properties and ability to survive in macrophages. We were able to compare the isogenic CD isolate in two states: virulent with high adhesive-invasive activity and ability to survive in macrophages, and non-virulent, when these properties are lost. In contrast to the CD isolate, passage of the laboratory strain K12 Mg1655 on the M9 medium supplemented with PA did not cause a similar effect. We performed a comparative proteomic analysis of membrane fractions isolated from ZvL2-PA and ZvL2-GLU using LC-MS. The laboratory strain K12 Mg1655 was used as a control.
Project description:The gastrointestinal tract is colonized by trillions of microorganisms collectively known as the gut microbiota. These microbes provide essential signals to support healthy gut function. The microbiota is separated from internal tissue by a single layer of intestinal epithelial cells that not only provides a physical barrier but also relays luminal signals to underlying gut immune cells. Altered microbiota composition including loss of anti-inflammatory microbes or outgrowth of mucosa-associated bacteria such as adherent-invasive E. coli (AIEC) are hallmarks of inflammatory disease including inflammatory bowel disease (IBD). In contrast to their hypothesized role in pathology, we recently identified select AIEC isolates that improve outcomes in mouse colitis models. These AIEC induce macrophage production of the anti-inflammatory cytokine IL-10 which limits gut inflammation and supports barrier repair. These benefits were lost if the AIEC was unable to attach to epithelial cells. However, the epithelial signaling underlying this protection remained unclear. To understand if intestinal epithelial cells signaled to immune cells after microbial attachment, we utilized human colonic organoid monolayers and found co-culture with a subset of AIEC isolates upregulated immune regulatory genes including CCL2, a macrophage recruiting chemokine. This effect was only observed in undifferenced epithelial cells, indicating epithelial stem cell recognition of microbes leads to macrophage recruitment. In vivo, antibody blockade of CCR2 abrogated the protective effect of AIEC colonization. Using bacterial transcriptome analysis, we identified high flagellin expression in AIEC isolates that activated epithelial signaling, with lost signaling in organoids deficient for TLR5, the receptor for flagellin. Together our findings suggest intestinal epithelial cells recognize microbial signals to coordinate macrophage recruitment that support intestinal repair, protecting from colitis.
Project description:The gastrointestinal tract is colonized by trillions of microorganisms collectively known as the gut microbiota. These microbes provide essential signals to support healthy gut function. The microbiota is separated from internal tissue by a single layer of intestinal epithelial cells that not only provides a physical barrier but also relays luminal signals to underlying gut immune cells. Altered microbiota composition including loss of anti-inflammatory microbes or outgrowth of mucosa-associated bacteria such as adherent-invasive E. coli (AIEC) are hallmarks of inflammatory disease including inflammatory bowel disease (IBD). In contrast to their hypothesized role in pathology, we recently identified select AIEC isolates that improve outcomes in mouse colitis models. These AIEC induce macrophage production of the anti-inflammatory cytokine IL-10 which limits gut inflammation and supports barrier repair. These benefits were lost if the AIEC was unable to attach to epithelial cells. However, the epithelial signaling underlying this protection remained unclear. To understand if intestinal epithelial cells signaled to immune cells after microbial attachment, we utilized human colonic organoid monolayers and found co-culture with a subset of AIEC isolates upregulated immune regulatory genes including CCL2, a macrophage recruiting chemokine. This effect was only observed in undifferenced epithelial cells, indicating epithelial stem cell recognition of microbes leads to macrophage recruitment. In vivo, antibody blockade of CCR2 abrogated the protective effect of AIEC colonization. Using bacterial transcriptome analysis, we identified high flagellin expression in AIEC isolates that activated epithelial signaling, with lost signaling in organoids deficient for TLR5, the receptor for flagellin. Together our findings suggest intestinal epithelial cells recognize microbial signals to coordinate macrophage recruitment that support intestinal repair, protecting from colitis.