Project description: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.
Project description:The intestinal anaerobic bacterium Akkermansia muciniphila is specialized in the degradation of mucins, which are heavily O-glycosylated proteins that constitute the major components of the mucus lining the intestine. Despite that adhesion to mucins is considered critical for the persistence of A. muciniphila in the human intestinal tract, our knowledge of how this intestinal symbiont recognizes and binds to mucins is still limited. Here, we first show that the mucin-binding properties of A. muciniphila are independent of environmental oxygen concentrations and not abolished by pasteurization. We then dissected the mucin-binding properties of pasteurized A. muciniphila by use of a recently developed cell-based mucin array that enables display of the tandem repeats of human mucins with distinct O-glycan patterns and structures. We found that A. muciniphila recognizes the unsialylated LacNAc (Galβ1-4GlcNAc1-R) disaccharide selectively on core2 and core3 O-glycans. This disaccharide epitope is abundantly found on human colonic mucins capped by sialic acids, and we demonstrated that endogenous A. muciniphila neuraminidase activity can uncover the epitope and promote binding. In summary, our study provides insights into the mucin-binding properties important for colonization of a key mucin-foraging bacterium.
Project description:Mice received TBI and allogeneic bone marrow transplantation. One group without and one group with T cells. On day 14 after transplantation mice were sacrificed and the intestinal tract was isolated. RNA was isolated from the intestinal tract of the two experimental groups.
Project description:The mammalian gastrointestinal tract harbors a diverse microbiota residing in intimate contact with the host immune system. Though most associations are symbiotic or commensal, some resident bacteria (termed pathobionts) have the potential to induce disease in immunocompromised hosts. Type VI secretion systems (T6SSs) have recently emerged as a novel mechanism for forging microbial-host interactions during infection. We reveal here a unique protective role for the T6SS of Helicobacter hepaticus, a Gram-negative bacterium of the murine intestinal microbiota. The T6SS of H. hepaticus targets effector substrates to intestinal epithelial cells (IECs). Mutants in T6SSs display higher intracellular and cell-associated numbers upon incubation with IECs, and exhibit increased bacterial colonization of the gastrointestinal tract compared to wild-type bacteria. The T6SS accordingly directs an anti-inflammatory gene expression profile in IECs co-cultured with H. hepaticus. Remarkably, T6SS mutants induce an exacerbated pro-inflammatory response in an experimental model of colitis. CD4+ T cells isolated from T6SS mutant-colonized animals produce increased T-helper 17 (Th17) cytokines in response to IECs presenting H. hepaticus antigens. These data demonstrate that H. hepaticus intimately interacts with IECs and employs type VI secretion to establish a balanced host relationship by limiting microbial colonization and intestinal inflammation. We propose that altering host-bacterial equilibriums that lead to dysbiosis of the microbiota contributes to human disorders such as inflammatory bowel disease and colon cancer.
Project description:Chlamydia trachomatis is an obligate intracellular Gram-negative bacterium that frequently causes an asymptomatic genital tract infection, gradually cleared by host immunity Transcriptome profiles were made of endometrial tissue from women with or without genital tract C. trachomatis infection, to characterize host responses to infection. Profiles showed that infection polarized host defense toward Type 2 immune responses. Responses included fibrin deposition, enhanced wound repair, and tissue remodeling. Trans-cervical endometrial biopsy specimens were collected from 10 women with no identified upper or lower genital tract infection and 12 women with C. trachomatis endometrial infection.