Characterization of Fusobacterium varium Fv113-g1 isolated from a patient with ulcerative colitis based on complete genome sequence and transcriptome analysis

Case-Control Study Examining the Composition of the Gut Microbiome in Individuals With and Without Immune-Mediated Dry Eye

PURPOSE

Gut microbiome alterations have been associated with various autoimmune diseases. There are limited data, however, on relationships between gut dysbiosis and immune-related dry eye (DE). Our aim was to compare the gut microbiome composition of individuals with early and late markers of Sjögren syndrome (SS) with controls without DE.

METHODS

We compared 20 individuals with positive early markers [antisalivary protein 1 (SP1), antiparotid secretory protein (PSP), anticarbonic anhydrase 6 (CA6) IgG, IgA, and IgM, n = 19)], or late markers (anti-Ro/SS-A and anti-La/SS-B, n = 1) of SS with no comorbid autoimmune diagnoses and 20 age-matched and sex-matched controls. Collected stool samples underwent deep RNA sequencing. The main outcomes measured included gut microbiome composition and diversity.

RESULTS

A total of 20 cases [Dry Eye Questionnaire-5 15.2 ± 3.4, Ocular Surface Disease Index 55.1 ± 22.8, and Schirmer 7.1 ± 5.2 mm] were compared with 20 controls (Dry Eye Questionnaire-5 4.8 ± 3.8, Ocular Surface Disease Index 14.2 ± 12.3, and Schirmer 20.4 ± 9.2 mm). No differences were observed in α-diversity ( P = 0.97) or overall community structure ( P = 0.62). Between groups, 32 species were differentially abundant ( P < 0.01). Among cases, 27 were relatively more abundant, including 10 Lactobacillus and 4 Bifidobacterium species. A relative depletion of 5 species was found in cases compared with controls, notably Fusobacterium varium and Prevotella stercorea .

CONCLUSIONS

Differences in gut microbiome composition were found in individuals with mostly early markers of SS compared with controls. However, their clinical significance to DE manifestations remains unclear. Further studies are needed to elucidate the role of gut dysbiosis on immune dysregulation and disease activity in the various forms of immune-mediated DE.

Gut microbes exacerbate systemic inflammation and behavior disorders in neurologic disease CADASIL

BACKGROUND

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a cerebral small vessel disease that carries mutations in NOTCH3. The clinical manifestations are influenced by genetic and environmental factors that may include gut microbiome.

RESULTS

We investigated the fecal metagenome, fecal metabolome, serum metabolome, neurotransmitters, and cytokines in a cohort of 24 CADASIL patients with 28 healthy household controls. The integrated-omics study showed CADASIL patients harbored an altered microbiota composition and functions. The abundance of bacterial coenzyme A, thiamin, and flavin-synthesizing pathways was depleted in patients. Neurotransmitter balance, represented by the glutamate/GABA (4-aminobutanoate) ratio, was disrupted in patients, which was consistent with the increased abundance of two major GABA-consuming bacteria, Megasphaera elsdenii and Eubacterium siraeum. Essential inflammatory cytokines were significantly elevated in patients, accompanied by an increased abundance of bacterial virulence gene homologs. The abundance of patient-enriched Fusobacterium varium positively correlated with the levels of IL-1β and IL-6. Random forest classification based on gut microbial species, serum cytokines, and neurotransmitters showed high predictivity for CADASIL with AUC = 0.89. Targeted culturomics and mechanisms study further showed that patient-derived F. varium infection caused systemic inflammation and behavior disorder in Notch3R170C/+ mice potentially via induction of caspase-8-dependent noncanonical inflammasome activation in macrophages.

CONCLUSION

These findings suggested the potential linkage among the brain-gut-microbe axis in CADASIL. Video Abstract.

Compositional alterations of the gut microbiota in acute myocardial infarction patients with type 2 diabetes mellitus

Background

Type 2 diabetes mellitus (T2DM) is a risk factor for acute myocardial infarction (AMI) and a common comorbidity in patients with AMI. T2DM doubles the fatality rate of patients with AMI in the acute phase of AMI and the follow-up period. However, the mechanisms by which T2DM increases the fatality rate remain unknown. This study sought to investigate changes in the gut microbiota of patients with AMI and T2DM (AMIDM) to extend understandings of the relative mechanisms from the aspects of gut microbiota.

Methods

Patients were recruited and divided into 2 groups comprising 15 patients with AMIDM and 15 patients with AMI but without T2DM (AMINDM). Their stool samples and clinical information were collected. 16S ribosomal DNA sequencing was used to analyze the structure and composition of the gut microbiota based on the operational taxonomic units.

Results

A significant difference was observed in the gut microbiota β diversity between the 2 groups. At the phylum level, the AMIDM patients showed an increase in the abundance of Firmicutes and a decrease in the abundance of Bacteroidetes compared to the AMINDM patients. At the genus level, the AMIDM patients showed an increase in the abundance of Companilactobacillus, Defluvitaleaceae UCG-011 and UCG-009, and a decrease in the abundance of Phascolarctobacterium and CAG 56 compared to the AMINDM patients. At the species level, the AMIDM patients showed an increase in the abundance of species unclassified NK4A214 group, Bacteroides clarus, Coprococcus comes, unclassified Defluviltaleaceae UCG-011, uncultured rumen bacterium, unclassified CAG 56, Barnesiella intestinihominis, Lachnospiraceae bacterium, Bacteroides nordii, unclassified UCG-009, and the Family XIII AD3011 group compared to the AMINDM patients. The gut microbiota function predictions indicated that the nucleotide metabolism-related pathway was significantly more increase in the patients with AMIDM than those with AMINDM. Additionally, the patients with AMIDM showed an increase in gram-positive bacteria and a decrease in the proportion of gram-negative bacteria. Our correlation analysis results on the gut microbiota and clinical parameters might extend understandings of the progression of AMI.

Conclusions

Changes in the gut microbiota composition of patients with AMIDM affect the severity of the metabolic disturbance and may be responsible for poorer clinical outcomes and worse disease progression in patients with AMIDM compared to those with AMINDM.

From adenoma to CRC stages: the oral-gut microbiome axis as a source of potential microbial and metabolic biomarkers of malignancy

BACKGROUND

Approximately 95% of Colorectal cancers (CRC) consist of adenocarcinomas originating from colonic Adenomatous polyps (AP). Increasing importance in CRC occurrence and progression has been attributed to the gut microbiota; however, a huge proportion of microorganisms inhabit the human digestive system. So, to comprehensively study the microbial spatial variations and their role in CRC progression, from AP to the different CRC phases, a holistic vision is imperative, including the simultaneous evaluation of multiple niches from the gastrointestinal system. Through an integrated approach, we identified potential microbial and metabolic biomarkers, able to discriminate human CRC from AP and/or also the different Tumor node metastasis (TNM) staging. In addition, as the microbiota contributes to the production of essential metabolic products detectable in fecal samples, we analysed and compared metabolites obtained from CRC and AP patients by using a Nuclear magnetic resonance (NMR) approach.

METHODS

In this observational study, saliva, tissue and stool samples from 61 patients, have been collected, including 46 CRC and 15 AP patients, age and sex-matched, undergoing surgery in 2018 at the Careggi University Hospital (Florence, Italy). First, the microbiota in the three-district between CRC and AP patients has been characterized, as well as in different CRC TNM stages. Subsequently, proton NMR spectroscopy has been used in combination with multivariate and univariate statistical approaches, to define the fecal metabolic profile of a restricted group of CRC and AP patients.

RESULTS

CRC patients display a different profile of tissue and fecal microbiota with respect to AP patients. Significant differences have been observed in CRC tissue microbial clades, with a rise of the Fusobacterium genus. In addition, significant taxa increase at the genus level has been observed in stool samples of CRC patients. Furthermore, Fusobacterium found in intestinal tissue has been positively correlated with fecal Parvimonas, for the first time. Moreover, as predicted by metagenomics pathway analysis, a significant increase of lactate (p=0.037) has been observed in the CRC fecal metabolic profiles, and positively correlated with Bifidobacterium (p=0.036). Finally, minor bacterial differences in CRC patients at stage T2 (TNM classification) have been detected, with a raise of the Spirochaetota phylum in CRC samples, with a slight increase of the Alphaproteobacteria class in fecal samples.

CONCLUSION

Our results suggest the importance of microbiota communities and oncometabolites in CRC development. Further studies on CRC/AP management with a focus on CRC assessment are needed to investigate novel microbial-related diagnostic tools aimed to improve therapeutic interventions.

Gastrointestinal disorders and intestinal bacteria: Advances in research and applications in therapy

Intestinal bacteria coexist with humans and play a role in suppressing the invasion of pathogens, producing short-chain fatty acids, producing vitamins, and controlling the immune system. Studies have been carried out on culturable bacterial species using bacterial culture methods for many years. However, as metagenomic analysis of bacterial genes has been developed since the 1990s, it has recently revealed that many bacteria in the intestine cannot be cultured and that approximately 1,000 species and 40 trillion bacteria are present in the gut microbiota. Furthermore, the composition of the microbiota is different in each disease state compared with the healthy state, and dysbiosis has received much attention as a cause of various diseases. Regarding gastrointestinal diseases, dysbiosis has been reported to be involved in inflammatory bowel disease, irritable bowel syndrome, and non-alcoholic steatohepatitis. Recent findings have also suggested that dysbiosis is involved in colon cancer, liver cancer, pancreatic cancer, esophageal cancer, and so on. This review focuses on the relationship between the gut microbiota and gastrointestinal/hepatobiliary diseases and also discusses new therapies targeting the gut microbiota.

Unexpected finding of Fusobacterium varium as the dominant Fusobacterium species in cattle rumen: potential implications for liver abscess etiology and interventions

Fusobacterium varium has been generally overlooked in cattle rumen microbiome studies relative to the presumably more abundant liver abscess-causing Fusobacterium necrophorum. However, F. varium was found to be more abundant in the rumen fluid of cattle and under culture conditions tailored to enrich F. necrophorum. Using near-full length 16S ribosomal ribonucleic acid sequencing, we demonstrate that F. varium grows under restrictive conditions commonly used to enumerate F. necrophorum, suggesting that previous F. necrophorum abundance assessment may have been inaccurate and that F. varium may be an underestimated member of the ruminal bacterial community. Fusobacterium varium were not as susceptible as F. necrophorum to in-feed antibiotics conventionally used in feedlots. Exposure to tylosin, the current gold standard for liver abscess reduction strategies in cattle, consistently hindered growth of the F. necrophorum strains tested by over 67% (P < 0.05) relative to the unexposed control. In contrast, F. varium strains were totally or highly resistant (0%-13% reduction in maximum yield, P < 0.05). Monensin, an ionophore antibiotic, had greater inhibitory activity against F. necrophorum than F. varium. Finally, preliminary genomic analysis of two F. varium isolates from the rumen revealed the presence of virulence genes related to those of pathogenic human F. varium isolates associated with active invasion of mammalian cells. The data presented here encourage further investigation into the ecological role of F. varium within the bovine rumen and potential role in liver abscess development, and proactive interventions.

New insights into bacterial mechanisms and potential intestinal epithelial cell therapeutic targets of inflammatory bowel disease

The global incidence of inflammatory bowel disease (IBD) has increased rapidly in recent years, but its exact etiology remains unclear. In the past decade, IBD has been reported to be associated with dysbiosis of gut microbiota. Although not yet proven to be a cause or consequence of IBD, the common hypothesis is that at least some alterations in the microbiome are protective or pathogenic. Furthermore, intestinal epithelial cells (IECs) serve as a protective physical barrier for gut microbiota, essential for maintaining intestinal homeostasis and actively contributes to the mucosal immune system. Thus, dysregulation within the intestinal epithelium increases intestinal permeability, promotes the entry of bacteria, toxins, and macromolecules, and disrupts intestinal immune homeostasis, all of which are associated with the clinical course of IBD. This article presents a selective overview of recent studies on bacterial mechanisms that may be protective or promotive of IBD in biological models. Moreover, we summarize and discuss the recent discovery of key modulators and signaling pathways in the IECs that could serve as potential IBD therapeutic targets. Understanding the role of the IECs in the pathogenesis of IBD may help improve the understanding of the inflammatory process and the identification of potential therapeutic targets to help ameliorate this increasingly common disease.

Elevated dietary carbohydrate and glycemic intake associate with an altered oral microbial ecosystem in two large U.S. cohorts

The human oral microbiome is associated with chronic diseases including cancer. However, our understanding of its relationship with diet is limited. We assessed the associations between carbohydrate and glycemic index (GI) with oral microbiome composition in 834 non-diabetic subjects from the NCI-PLCO and ACS-CPSII cohorts. The oral microbiome was characterized using 16Sv3-4 rRNA-sequencing from oral mouthwash samples. Daily carbohydrate and GI were assessed from food frequency questionnaires. We used linear regression, permutational MANOVA, and negative binomial Generalized Linear Models (GLM) to test associations of diet with α- and β-diversity and taxon abundance (adjusting for age, sex, cohort, BMI, smoking, caloric intake, and alcohol). A q-value (FDR-adjusted P-value) of <0.05 was considered significant. Oral bacterial α-diversity trended higher in participants in the highest quintiles of carbohydrate intake, with marginally increased richness and Shannon diversity (p-trend=0.06 and 0.07). Greater carbohydrate intake was associated with greater abundance of class Fusobacteriia (q=0.02) and genus Leptotrichia (q=0.01) and with lesser abundance of an Actinomyces OTU (q=4.7E-04). Higher GI was significantly related to greater abundance of genus Gemella (q=0.001). This large, nationwide study provides evidence that diets high in carbohydrates and GI may influence the oral microbiome.

Do we need to change our perspective about gut biomarkers? A public data mining approach to identify differentially abundant bacteria in intestinal inflammatory diseases

Introduction

The gut microbiome is involved in multiple processes that influence host physiology, and therefore, disruptions in microbiome homeostasis have been linked to diseases or secondary infections. Given the importance of the microbiome and the communities of microorganisms that compose it (microbiota), the term biomarkers were coined, which are bacteria correlated with disease states, diets, and the lifestyle of the host. However, a large field in the study of intestinal biomarkers remains unexplored because the bacterial communities associated with a given disease state have not been exactly defined yet.

Methods

Here, we analyzed public data of studies focused on describing the intestinal microbiota of patients with some intestinal inflammatory diseases together with their respective controls. With these analyses, we aimed to identify differentially abundant bacteria between the subjects with the disease and their controls.

Results

We found that frequently reported bacteria such as Fusobacterium, Streptococcus, and Escherichia/Shigella were differentially abundant between the groups, with a higher abundance mostly in patients with the disease in contrast with their controls. On the other hand, we also identified potentially beneficial bacteria such as Faecalibacterium and Phascolarctobacterium, with a higher abundance in control patients.

Discussion

Our results of the differentially abundant bacteria contrast with what was already reported in previous studies on certain inflammatory diseases, but we highlight the importance of considering more comprehensive approaches to redefine or expand the definition of biomarkers. For instance, the intra-taxa diversity within a bacterial community must be considered, as well as environmental and genetic factors of the host, and even consider a functional validation of these biomarkers through in vivo and in vitro approaches. With the above, these key bacterial communities in the intestinal microbiota may have potential as next-generation probiotics or may be functional for the design of specific therapies in certain intestinal diseases.

Fucosyltransferase 2: A Genetic Risk Factor for Intestinal Diseases

The fucosyltransferase 2 gene (FUT2) mediates the synthesis of histoblood group antigens (HBGA) that occur in vivo from multiple organs, particularly on the surface of intestinal epithelial cells and body fluids. To date, many studies have demonstrated that the interaction of HBGA with the host microbiota is the cause of pathogenesis of intestinal diseases, making FUT2 non-secretor a risk factor for inflammatory bowel disease (IBD) due to the lack of HBGA. As HBGA also acts as an attachment site for norovirus (NoV) and rotavirus (RV), the non-secretor becomes a protective factor for both viral infections. In addition, the interaction of norovirus and rotavirus with symbiotic bacteria has been found to play an important role in regulating enteroviral infection in IBD. Given the current incomplete understanding of the complex phenomenon and the underlying pathogenesis of intestinal diseases such as IBD, it has recently been hypothesized that the FUT2 gene regulates intestinal bacteria through attachment sites, may help to unravel the role of FUT2 and intestinal flora in the mechanism of intestinal diseases in the future, and provide new ideas for the prevention and treatment of intestinal diseases through more in-depth studies.

Periodontitis Exacerbates and Promotes the Progression of Chronic Kidney Disease Through Oral Flora, Cytokines, and Oxidative Stress

Periodontitis is a type of systemic immune inflammation that is caused by the complex infection of a variety of microorganisms in the subgingival plaque and the imbalance of the microbial ecological environment in the mouth. Periodontitis and chronic kidney disease (CKD) share many risk factors, such as obesity, smoking, and age. A growing body of data supports a strong correlation between periodontitis and kidney disease. Evidence supports the role of periodontal inflammation and elevated serum inflammatory mediators in renal atherosclerosis, renal deterioration, and end-stage renal disease (ESRD) development. Periodontitis is a risk factor for kidney disease. However, to our knowledge, there are few studies detailing the possible link between periodontitis and CKD. This review summarizes the possible mechanisms underlying periodontitis and CKD. More importantly, it highlights novel and potential pathogenic factors for CKD, including bacteria, pro-inflammatory mediators and oxidative stress. However, most research on the relationship between periodontitis and systemic disease has not determined causality, and these diseases are largely linked by bidirectional associations. Future research will focus on exploring these links to contribute to new treatments for CKD.

Classification of Changes in the Fecal Microbiota Associated with Colonic Adenomatous Polyps Using a Long-Read Sequencing Platform

The microbiota is the community of microorganisms that colonizes the oral cavity, respiratory tract, and gut of multicellular organisms. The microbiota exerts manifold physiological and pathological impacts on the organism it inhabits. A growing body of attention is being paid to host–microbiota interplay, which is highly relevant to the development of carcinogenesis. Adenomatous polyps are considered a common hallmark of colorectal cancer, the second leading cause of carcinogenesis-mediated death worldwide. In this study, we examined the relevance between targeted operational taxonomic units and colonic polyps using short- and long-read sequencing platforms. The gut microbiota was assessed in 132 clinical subjects, including 53 healthy participants, 36 patients with occult blood in the gut, and 43 cases with adenomatous polyps. An elevation in the relative abundance of Klebsiella pneumonia, Fusobacterium varium, and Fusobacterium mortiferum was identified in patients with adenomatous polyps compared with the other groups using long-read sequencing workflow. In contrast, the relatively high abundances of Blautia luti, Bacteroides plebeius, and Prevotella copri were characterized in the healthy groups. The diversities in gut microbiota communities were similar in all recruited samples. These results indicated that alterations in gut microbiota were characteristic of participants with adenomatous polyps, which might be relevant to the further development of CRC. These findings provide a potential contribution to the early prediction and interception of CRC occurrence.

Immunometabolism, Micronutrients, and Bariatric Surgery: The Use of Transcriptomics and Microbiota-Targeted Therapies

BACKGROUND

Obesity is associated with the gut microbiota and decreased micronutrient status. Bariatric surgery is a recommended therapy for obesity. It can positively affect the composition of the gut bacteria but also disrupt absorption of nutrients. Low levels of micronutrients can affect metabolic processes, like glycolysis, TCA cycle, and oxidative phosphorylation, that are associated with the immune system also known as immunometabolism.

METHODS

MEDLINE, PUBMED, and Google Scholar were searched. Articles involving gut microbiome, micronutrient deficiency, gut-targeted therapies, transcriptome analysis, micronutrient supplementation, and bariatric surgery were included.

RESULTS

Studies show that micronutrients play a pivotal role in the intestinal immune system and regulating immunometabolism. Research demonstrates that gut-targeting therapies may improve the microbiome health for bariatric surgery populations. There is limited research that examines the role of micronutrients in modulating the gut microbiota among the bariatric surgery population.

CONCLUSIONS

Investigations are needed to understand the influence that micronutrient deficiencies have on the gut, particularly immunometabolism. Nutritional transcriptomics shows great potential in providing this type of analysis to develop gut-modulating therapies as well as more personalized nutrition recommendations for bariatric surgery patients.

Mucosal microbiota and gene expression are associated with long-term remission after discontinuation of adalimumab in ulcerative colitis

Given that sustained remission is the ultimate treatment goal in the management of patients with ulcerative colitis (UC), the decision to stop anti-tumor necrosis factor (anti-TNF) treatment in UC patients is difficult. The aim of this study was to evaluate mucosal microbiota and gene expression profiles associated with long-term remission after discontinuation of anti-TNF therapy. In nine UC patients who received anti-TNF therapy for 6 months, microbiota isolated from uninflamed mucosae and gene expression in inflamed and uninflamed mucosae were investigated at week 0 and at week 24. At treatment initiation, Fusobacterium sp. and Veillonella dispar were over-represented in the relapse group compared with the non-relapse group. After treatment, Dorea sp. and Lachnospira sp. were over-represented in the non-relapse group. In the relapse group only, a significant shift in gut bacterial community composition was found between week 0 and week 24. Gene expression of ALIX (PDCD6IP) and SLC9A3 was significantly higher in the non-relapse group than in the relapse group. Lastly, we used machine learning methods to identify relevant gene signatures associated with sustained remission. Statistical analyses of microbiota and expression profiles revealed differences between UC patients who did or did not keep remission after the discontinuation of TNF inhibitors.

Trial registration: UMIN000020785: Evaluation of adalimumab therapy in mesalazine-resistant or -intolerant ulcerative colitis; an observational study (EARLY study).

Southern Chinese populations harbour non-nucleatum Fusobacteria possessing homologues of the colorectal cancer-associated FadA virulence factor

OBJECTIVE

Fusobacteria are not common nor relatively abundant in non-colorectal cancer (CRC) populations, however, we identified multiple Fusobacterium taxa nearly absent in western and rural populations to be comparatively more prevalent and relatively abundant in southern Chinese populations. We investigated whether these represented known or novel lineages in the Fusobacterium genus, and assessed their genomes for features implicated in development of cancer.

METHODS

Prevalence and relative abundances of fusobacterial species were calculated from 3157 CRC and non-CRC gut metagenomes representing 16 populations from various biogeographies. Microbial genomes were assembled and compared with existing reference genomes to assess novel fusobacterial diversity. Phylogenetic distribution of virulence genes implicated in CRC was investigated.

RESULTS

Irrespective of CRC disease status, southern Chinese populations harboured increased prevalence (maximum 39% vs 7%) and relative abundances (average 0.4% vs 0.04% of gut community) of multiple recognised and novel fusobacterial taxa phylogenetically distinct from Fusobacterium nucleatum. Genomes assembled from southern Chinese gut metagenomes increased existing fusobacterial diversity by 14.3%. Homologues of the FadA adhesin linked to CRC were consistently detected in several monophyletic lineages sister to and inclusive of F. varium and F. ulcerans, but not F. mortiferum. We also detected increased prevalence and relative abundances of F. varium in CRC compared with non-CRC cohorts, which together with distribution of FadA homologues supports a possible association with gut disease.

CONCLUSION

The proportion of fusobacteria in guts of southern Chinese populations are higher compared with several western and rural populations in line with the notion of environment/biogeography driving human gut microbiome composition. Several non-nucleatum taxa possess FadA homologues and were enriched in CRC cohorts; whether this imposes a risk in developing CRC and other gut diseases deserves further investigation.

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.

Metagenomic analyses of the gut microbiota associated with colorectal adenoma

Recent studies have suggested an association between certain members of the Fusobacterium genus, especially F. nucleatum, and the progression of advanced colorectal carcinoma (CRC). We assessed such an association of the gut microbiota in Japanese patients with colorectal adenoma (CRA) or intramucosal CRC using colonoscopy aspirates. We analyzed samples from 81 Japanese patients, including 47 CRA and 24 intramucosal CRC patients, and 10 healthy subjects. Metagenomic analysis of the V3-V4 region of the 16S ribosomal RNA gene was performed. The linear discriminant analysis (LDA) effect size (LEfSe) method was used to examine microbial dysbiosis, revealing significant differences in bacterial abundances between the healthy controls and CRA or intramucosal CRC patients. In particular, F. varium was statistically more abundant in patients with CRA and intramucosal CRC than in healthy subjects. Here, we present the metagenomic profile of CRA and intramucosal CRC and demonstrate that F. varium is at least partially involved in the pathogenesis of CRA and intramucosal CRC.

Fusobacterium and Colorectal Cancer

Colorectal cancer (CRC) is the third most common cancer worldwide and its pathogenesis has been extensively explored over the past decades. Recently, microorganisms in the gastrointestinal tract have emerged as potential etiological agents. In particular, a direct proportional association between Fusobacterium and CRC has been described. Since then, the functional impact of Fusobacterium in CRC development has been studied using various mouse models. Although some epidemiologic studies did not establish an obvious relationship between Fusobacterium and CRC, numerous pathogenic mechanisms leading to the disease have been described. For instance, Fusobacterium can activate the E-cadherin/β-catenin signaling pathway and is associated with particular epigenetic phenotype, such as microsatellite instability (MSI) and hypermethylation, via its strong adhesive and invasive abilities resulting in malignant transformation of epithelial cells. Also, Fusobacterium could alter the tumor microenvironment (TME) significantly by myeloid-derived suppressor cells (MDSCs), tumor associated macrophages (TAMs), and tumor associated neutrophils (TANs) recruitment and local immune suppression. Herein, we provide an in-depth review of the relationship between Fusobacterium and colorectal cancer. In light of the emergence of microbiome-based therapeutics, potential therapies and preventive strategies for colorectal cancer related to Fusobacterium are also discussed.

Reduction of Fumarate to Succinate Mediated by Fusobacterium varium

Accumulation of succinate as a fermentation product of Fusobacterium varium was enhanced when the anaerobic bacterium was grown on complex peptone medium supplemented with fumarate. Residual substrates and fermentation products were determined by proton NMR spectroscopy. Cells collected from the fumarate-supplemented medium (8-10 h after inoculation) supported the conversion of fumarate to succinate when suspended with fumarate and a co-substrate (glucose, sorbitol, or glycerol). Succinate production was limited by the availability of fumarate or reducing equivalents supplied by catabolism of a co-substrate via the Embden-Meyerhof-Parnas (EMP) pathway. The choice of reducing co-substrate influenced the yield of acetate and lactate as side products. High conversions of fumarate to succinate were achieved over pH 6.6-8.2 and initial fumarate concentrations up to 300 mM. However, at high substrate concentrations, intracellular retention of succinate reduced extracellular yields. Overall, the efficient utilization of fumarate (≤ 400 mM) combined with the significant extracellular accumulation of succinate (corresponding to ≥ 70% conversion) indicated the effective utilization of fumarate as a terminal electron acceptor by F. varium and the potential of the methodology for the bioproduction of succinate.