Helicobacter bilis Infection Alters Mucosal Bacteria and Modulates Colitis Development in Defined Microbiota Mice

Spatial host-microbiome sequencing reveals niches in the mouse gut

Mucosal and barrier tissues, such as the gut, lung or skin, are composed of a complex network of cells and microbes forming a tight niche that prevents pathogen colonization and supports host-microbiome symbiosis. Characterizing these networks at high molecular and cellular resolution is crucial for understanding homeostasis and disease. Here we present spatial host-microbiome sequencing (SHM-seq), an all-sequencing-based approach that captures tissue histology, polyadenylated RNAs and bacterial 16S sequences directly from a tissue by modifying spatially barcoded glass surfaces to enable simultaneous capture of host transcripts and hypervariable regions of the 16S bacterial ribosomal RNA. We applied our approach to the mouse gut as a model system, used a deep learning approach for data mapping and detected spatial niches defined by cellular composition and microbial geography. We show that subpopulations of gut cells express specific gene programs in different microenvironments characteristic of regional commensal bacteria and impact host-bacteria interactions. SHM-seq should enhance the study of native host-microbe interactions in health and disease.

Ketogenic Diet Has Moderate Effects on the Fecal Microbiota of Wild-Type Mice

The ketogenic diet (KD) is a high-fat, low-carbohydrate diet that has been reported to have neuroprotective effects. The health effects of KD might be linked to an altered gut microbiome, which plays a major role in host health, leading to neuroprotective effects via the gut-brain axis. However, results from different studies, most often based on the 16S rRNA gene and metagenome sequencing, have been inconsistent. In this study, we assessed the effect of a 4-week KD compared to a western diet (WD) on the colonic microbiome of female C57Bl/6J mice by analyzing fecal samples using fluorescence in situ hybridization. Our results showed distinct changes in the total number of gut bacteria following the 4-week KD, in addition to changes in the composition of the microbiome. KD-fed mice showed higher absolute numbers of Actinobacteria (especially Bifidobacteria spp.) and lower absolute levels of Proteobacteria, often linked to gut inflammation, in comparison with WD-fed mice. Furthermore, an increased abundance of the typically rare genus Atopobium was observed. These changes may indicate the possible anti-inflammatory effects of the KD. However, since the overall changes in the microbiota seem low, the KD effects might be linked to the differential abundance of only a few key genera in mice.

Resources to Facilitate Use of the Altered Schaedler Flora (ASF) Mouse Model to Study Microbiome Function

Animals colonized with a defined microbiota represent useful experimental systems to investigate microbiome function. The altered Schaedler flora (ASF) represents a consortium of eight murine bacterial species that have been used for more than 4 decades where the study of mice with a reduced microbiota is desired. In contrast to germ-free mice, or mice colonized with only one or two species, ASF mice show the normal gut structure and immune system development. To further expand the utility of the ASF, we have developed technical and bioinformatic resources to enable a systems-based analysis of microbiome function using this model. Here, we highlighted four distinct applications of these resources that enable and improve (i) measurements of the abundance of each ASF member by quantitative PCR; (ii) exploration and comparative analysis of ASF genomes and the metabolic pathways they encode that comprise the entire gut microbiome; (iii) global transcriptional profiling to identify genes whose expression responds to environmental changes within the gut; and (iv) discovery of genetic changes resulting from the evolutionary adaptation of the microbiota. These resources were designed to be accessible to a broad community of researchers that, in combination with conventionally-reared mice (i.e., with complex microbiome), should contribute to our understanding of microbiome structure and function. IMPORTANCE Improved experimental systems are needed to advance our understanding of how the gut microbiome influences processes of the mammalian host as well as microbial community structure and function. An approach that is receiving considerable attention is the use of animal models that harbor a stable microbiota of known composition, i.e., defined microbiota, which enables control over an otherwise highly complex and variable feature of mammalian biology. The altered Schaedler flora (ASF) consortium is a well-established defined microbiota model, where mice are stably colonized with 8 distinct murine bacterial species. To take better advantage of the ASF, we established new experimental and bioinformatics resources for researchers to make better use of this model as an experimental system to study microbiome function.

Helicobacter bilis Contributes to the Occurrence of Inflammatory Bowel Disease by Inducing Host Immune Disorders

Gut microbiota coevolve with humans to achieve a symbiotic relationship, which ultimately leads to physiological homeostasis. A variety of diseases can occur once this balance is disrupted. Helicobacter bilis (H. bilis) is an opportunistic pathogen in humans, triggering multiple diseases, including inflammatory bowel disease (IBD). IBD is a chronic immunologically mediated inflammation of the human gastrointestinal tract, and its occurrence is closely related to the gut microbiota. Several studies have demonstrated that H. bilis colonization is associated with IBD, and its mechanism is related to host immunity. However, few studies have investigated these mechanisms of action. Therefore, this article is aimed at reviewing these studies and summarizing the mechanisms of H. bilis-induced IBD from two perspectives: adaptive immunity and innate immunity. Furthermore, this study provides a preliminary discussion on treating H. bilis-related IBD. In addition, we also demonstrated that H. bilis played an important role in promoting the carcinogenesis of IBD and discussed its mechanism.

Helicobacter bilis infection induces oxidative stress in and enhances the proliferation of human cholangiocytes

BACKGROUND

Helicobacter bilis, an enterohepatic Helicobacter species, represents a carcinogenic risk factor for cholangiocytes owing to the prevalence of infections in patients with biliary tract cancer, cholecystitis, and pancreaticobiliary maljunction. However, the effect of H. bilis infection on cholangiocytes and the process and mechanism of carcinogenesis are not known. We aimed to determine the effects of H. bilis on cholangiocytes, focusing on inflammation and oxidative stress.

MATERIALS AND METHODS

Helicobacter bilis and MMNK-1 cells were cocultured for 24 h and inflammatory cytokine secretion was evaluated. Furthermore, MMNK-1 cell proliferation, intracellular reactive oxidant species (ROS) production, and DNA damage caused by ROS were investigated. All factors were compared with and without H. bilis infection.

RESULTS

Interleukin (IL)-6 and IL-8 secretion were significantly increased in MMNK-1 cocultures with H. bilis (IL-6, 24.3 ± 12.2 vs. 271.1 ± 286.4 pg/ml; IL-8, 167.6 ± 78.7 vs. 1085.1 ± 1047.1 pg/ml, p < .05). MMNK-1 proliferation was also significantly higher in H. bilis cocultures (1.05 ± 0.02 vs. 1.00-fold, respectively; p < .05). Coculturing enhanced the production of ROS in MMNK-1 cells depending on the cell concentration of H. bilis (1.0 vs. 1.17 ± 0.06, p < .05); however, DNA injury was not observed in cocultures with H. bilis (5.35 ± 0.87 vs. 6.08 ± 0.55 pg/μl, p = .06).

CONCLUSIONS

Helicobacter bilis infection induced ROS production in and enhanced the proliferation of cholangiocytes.

Vertical transmission of attaching and invasive E. coli from the dam to neonatal mice predisposes to more severe colitis following exposure to a colitic insult later in life

The gastrointestinal microbiota begins to be acquired at birth and continually matures through early adolescence. Despite the relevance for gut health, few studies have evaluated the impact of pathobiont colonization of neonates on the severity of colitis later in life. LF82 is an adherent invasive E. coli strain associated with ileal Crohn’s disease. The aim of this study was to evaluate the severity of dextran sodium sulfate (DSS)-induced colitis in mice following E. coli LF82 colonization. Gnotobiotic mice harboring the altered Schaedler flora (ASF) were used as the model. While E. coli LF82 is neither adherent nor invasive, it was been demonstrated that adult ASF mice colonized with E. coli LF82 develop more severe DSS-induced colitis compared to control ASF mice treated with DSS. Therefore, we hypothesized that E. coli LF82 colonization of neonatal ASF mice would reduce the severity of DSS-induced inflammation compared to adult ASF mice colonized with E. coli LF82. To test this hypothesis, adult ASF mice were colonized with E. coli LF82 and bred to produce offspring (LF82_N) that were vertically colonized with LF82. LF82_N and adult-colonized (LF82_A) mice were given 2.0% DSS in drinking water for seven days to trigger colitis. More severe inflammatory lesions were observed in the LF82_N + DSS mice when compared to LF82_A + DSS mice, and were characterized as transmural in most of the LF82_N + DSS mice. Colitis was accompanied by secretion of proinflammatory cytokines (IFNγ, IL-17) and specific mRNA transcripts within the colonic mucosa. Using 16S rRNA gene amplicon sequencing, LF82 colonization did not induce significant changes in the ASF community; however, minimal changes in spatial redistribution by fluorescent in situ hybridization were observed. These results suggest that the age at which mice were colonized with E. coli LF82 pathobiont differentially impacted severity of subsequent colitic events.

The Intestinal Microbiota May Be a Potential Theranostic Tool for Personalized Medicine

The human intestine is colonized by a huge number of microorganisms from the moment of birth. This set of microorganisms found throughout the human body, is called the microbiota; the microbiome indicates the totality of genes that the microbiota can express, i.e., its genetic heritage. Thus, microbiota participates in and influences the proper functioning of the organism. The microbiota is unique for each person; it differs in the types of microorganisms it contains, the number of each microorganism, and the ratio between them, but mainly it changes over time and under the influence of many factors. Therefore, the correct functioning of the human body depends not only on the expression of its genes but also on the expression of the genes of the microorganisms it coexists with. This fact makes clear the enormous interest of community science in studying the relationship of the human microbiota with human health and the incidence of disease. The microbiota is like a unique personalized “mold” for each person; it differs quantitatively and qualitatively for the microorganisms it contains together with the relationship between them, and it changes over time and under the influence of many factors. We are attempting to modulate the microbial components in the human intestinal microbiota over time to provide positive feedback on the health of the host, from intestinal diseases to cancer. These interventions to modulate the intestinal microbiota as well as to identify the relative microbiome (genetic analysis) can range from dietary (with adjuvant prebiotics or probiotics) to fecal transplantation. This article researches the recent advances in these strategies by exploring their advantages and limitations. Furthermore, we aim to understand the relationship between intestinal dysbiosis and pathologies, through the research of resident microbiota, that would allow the personalization of the therapeutic antibiotic strategy.

Genetic and environmental factors shape the host response to Helicobacter hepaticus: insights into IBD pathogenesis

Pathobionts are members of the gut microbiota with the capacity to cause disease when there is malfunctioning intestinal homeostasis. These organisms are thought to be major contributors to the pathogenesis of inflammatory bowel disease (IBD), a group of chronic inflammatory disorders driven by dysregulated responses towards the microbiota. Over two decades have passed since the discovery of Helicobacter hepaticus, a mouse pathobiont which causes colitis in the context of immune deficiency. During this time, we have developed a detailed understanding of the cellular players and cytokine networks which drive H. hepaticus immunopathology. However, we are just beginning to understand the microbial factors that enable H. hepaticus to interact with the host and influence colonic health and disease. Here we review key H. hepaticus-host interactions, their relevance to other exemplar pathobionts and how when maladapted they drive colitis. Further understanding of these pathways may offer new therapeutic approaches for IBD.

Tumor necrosis factor ligand-related molecule 1A affects the intestinal mucosal barrier function by promoting Th9/interleukin-9 expression

Objectives

To investigate the effect of tumor necrosis factor ligand-related molecule 1A (TL1A) on the intestinal mucosal barrier in mice with chronic colitis.

Methods

Male TL1A-overexpressing transgenic mice and male C57BL/6 wild-type mice were used to establish a dextran sodium sulfate (DSS)-induced colitis model. The expression of occludin and claudin-1 was observed. Bacterial distribution in the intestinal mucosa and Th9/interleukin (IL)-9 expression were detected. In vitro co-culture systems of naive CD4⁺ T cells and Caco-2 cells were established and TL1A was added. Changes in transepithelial electrical resistance and IL-9 expression were measured. CD4+IL-9 cells were detected by flow cytometry.

Results

DSS mice showed a significant down-regulation of occludin and claudin-1 compared with controls. Expression levels of occludin, zonulin-1, and claudin-1 in the Caco-2+TGF-β+IL-4+TL1A group were significantly lower than in the Caco-2+TGF-β+IL-4 group. Bacterial distribution was clearly disordered in the DSS group. Transmembrane resistance of the Caco-2+TGF-β+IL-4+TL1A group was significantly lower and IL-9 expression significantly higher than in the Caco-2+TGF-β+IL-4 group.

Conclusions

TL1A overexpression promotes destruction of the intestinal mucosal barrier in mice with chronic colitis. The underlying mechanism may be associated with the promoting role of TL1A in Th9/IL-9 expression, which further destroys the mucosal barrier.

Association of Helicobacter bilis Infection with the Development of Colorectal Cancer

The role of Helicobacter_bilis (H.bilis) in the development of inflammatory bowel disease (IBD) and colitis-associated carcinogenesis (CAC) has seldom been investigated. We examined the abundance of H.bilis in 58 colorectal cancers (CRCs), 20 IBDs, 40 cases of normal colorectal mucosa (NCs), and 20 adenomas (ADs) by 16S rRNA fluorescence in situ hybridization (FISH). Number of CD4⁺CD45RB⁺T cell and expression of IFN-γ and TNF-α in these tissues was determined by immunofluorescence. The abundance of H.bilis was significantly higher in CRCs than that in IBDs (P = 0.006), ADs (P < 0.001) and NCs (P < 0.0001). The abundance of H.bilis in IBDs was significantly higher than that in ADs (P = 0.013). Moreover, the average number of CD4⁺CD45RB⁺T cell was significantly higher in CRCs than that in IBDs (P = 0.017) and NCs (P = 0.009). In addition, there was a positive correlation between the H.bilis abundance and density of CD4⁺CD45RB⁺T cells in 30 colorectal tissues (P < 0.0001). The frequency of co-staining for CD4⁺CD45RB⁺T cells and IFN-γ was significantly higher in H.bilis positive group than that in H.bilis negative group (P = 0.002). H.bilis may play a role in the initiation of IBD and CAC, possibly through promoting the transformation of T cells into CD4⁺CD45RB⁺T cells and increasing the expression of proinflammatory cytokines IFN-γ.

The microbiome in inflammatory bowel diseases: from pathogenesis to therapy

Inflammatory bowel disease (IBD) has become a global disease with accelerating incidence worldwide in the 21st century while its accurate etiology remains unclear. In the past decade, gut microbiota dysbiosis has consistently been associated with IBD. Although many IBD-associated dysbiosis have not been proven to be a cause or an effect of IBD, it is often hypothesized that at least some of alteration in microbiome is protective or causative. In this article, we selectively reviewed the hypothesis supported by both association studies in human and pathogenesis studies in biological models. Specifically, we reviewed the potential protective bacterial pathways and species against IBD, as well as the potential causative bacterial pathways and species of IBD. We also reviewed the potential roles of some members of mycobiome and virome in IBD. Lastly, we covered the current status of therapeutic approaches targeting microbiome, which is a promising strategy to alleviate and cure this inflammatory disease.

Utilizing Whole Fusobacterium Genomes To Identify, Correct, and Characterize Potential Virulence Protein Families

Fusobacterium spp. are Gram-negative, anaerobic, opportunistic pathogens involved in multiple diseases, including a link between the oral pathogen Fusobacterium nucleatum and the progression and severity of colorectal cancer. The identification and characterization of virulence factors in the genus Fusobacterium has been greatly hindered by a lack of properly assembled and annotated genomes. Using newly completed genomes from nine strains and seven species of Fusobacterium, we report the identification and corrected annotation of verified and potential virulence factors from the type 5 secreted autotransporter, FadA, and MORN2 protein families, with a focus on the genetically tractable strain F. nucleatum subsp. nucleatum ATCC 23726 and type strain F. nucleatum subsp. nucleatum ATCC 25586. Within the autotransporters, we used sequence similarity networks to identify protein subsets and show a clear differentiation between the prediction of outer membrane adhesins, serine proteases, and proteins with unknown function. These data have identified unique subsets of type 5a autotransporters, which are key proteins associated with virulence in F. nucleatum However, we coupled our bioinformatic data with bacterial binding assays to show that a predicted weakly invasive strain of F. necrophorum that lacks a Fap2 autotransporter adhesin strongly binds human colonocytes. These analyses confirm a gap in our understanding of how autotransporters, MORN2 domain proteins, and FadA adhesins contribute to host interactions and invasion. In summary, we identify candidate virulence genes in Fusobacterium, and caution that experimental validation of host-microbe interactions should complement bioinformatic predictions to increase our understanding of virulence protein contributions in Fusobacterium infections and disease.IMPORTANCE Fusobacterium spp. are emerging pathogens that contribute to mammalian and human diseases, including colorectal cancer. Despite a validated connection with disease, few proteins have been characterized that define a direct molecular mechanism for Fusobacterium pathogenesis. We report a comprehensive examination of virulence-associated protein families in multiple Fusobacterium species and show that complete genomes facilitate the correction and identification of multiple, large type 5a secreted autotransporter genes in previously misannotated or fragmented genomes. In addition, we use protein sequence similarity networks and human cell interaction experiments to show that previously predicted noninvasive strains can indeed bind to and potentially invade human cells and that this could be due to the expansion of specific virulence proteins that drive Fusobacterium infections and disease.

Other Helicobacters, gastric and gut microbiota

The current article is a review of the most important and relevant literature published in 2016 and early 2017 on non-Helicobacter pylori Helicobacter infections in humans and animals, as well as interactions between H. pylori and the microbiota of the stomach and other organs. Some putative new Helicobacter species were identified in sea otters, wild boars, dogs, and mice. Many cases of Helicobacter fennelliae and Helicobacter cinaedi infection have been reported in humans, mostly in immunocompromised patients. Mouse models have been used frequently as a model to investigate human Helicobacter infection, although some studies have investigated the pathogenesis of Helicobacters in their natural host, as was the case for Helicobacter suis infection in pigs. Our understanding of both the gastric and gut microbiome has made progress and, in addition, interactions between H. pylori and the microbiome were demonstrated to go beyond the stomach. Some new approaches of preventing Helicobacter infection or its related pathologies were investigated and, in this respect, the probiotic properties of Saccharomyces, Lactobacillus and Bifidobacterium spp. were confirmed.

A real-time PCR assay for accurate quantification of the individual members of the Altered Schaedler Flora microbiota in gnotobiotic mice

Changes in the gastrointestinal microbial community are frequently associated with chronic diseases such as Inflammatory Bowel Diseases. However, understanding the relationship of any individual taxon within the community to host physiology is made complex due to the diversity and individuality of the gut microbiota. Defined microbial communities such as the Altered Schaedler Flora (ASF) help alleviate the challenges of a diverse microbiota by allowing one to interrogate the relationship between individual bacterial species and host responses. An important aspect of studying these relationships with defined microbial communities is the ability to measure the population abundance and dynamics of each member. Herein, we describe the development of an improved ASF species-specific and sensitive real-time quantitative polymerase chain reaction (qPCR) for use with SYBR Green chemistry to accurately assess individual ASF member abundance. This approach targets hypervariable regions V1 through V3 of the 16S rRNA gene of each ASF taxon to enhance assay specificity. We demonstrate the reproducibility, sensitivity and application of this new method by quantifying each ASF bacterium in two inbred mouse lines. We also used it to assess changes in ASF member abundance before and after acute antibiotic perturbation of the community as well as in mice fed two different diets. Additionally, we describe a nested PCR assay for the detection of lowly abundant ASF members. Altogether, this improved qPCR method will facilitate gnotobiotic research involving the ASF community by allowing for reproducible quantification of its members under various physiological conditions.