Molecular characterization of the microbial species that colonize human ileal and colonic mucosa by using 16S rDNA sequence analysis

The role of kynurenine pathway metabolism mediated by exercise in the microbial-gut-brain axis in Alzheimer's disease

In recent years, the role of the microbiome-gut-brain axis in the pathogenesis of Alzheimer's disease (AD) has garnered increasing attention. Specifically, tryptophan metabolism via the kynurenine pathway (KP) plays a crucial regulatory role in this axis. This study reviews how exercise regulates the microbiome-gut-brain axis by influencing kynurenine pathway metabolism, thereby exerting resistance against AD. This paper also discusses how exercise positively impacts AD via the microbiome-gut-brain axis by modulating the endocrine, autonomic nervous, and immune systems. Although the specific mechanisms are not fully understood, research indicates that exercise may optimize tryptophan metabolism by promoting the growth of beneficial microbiota and inhibiting harmful microbiota, producing substances that are beneficial to the nervous system and combating AD. The aim of this review is to provide new perspectives and potential intervention strategies for the prevention and treatment of AD by exploring the links between exercise, KP and the gut-brain axis.

Delving the depths of 'terra incognita' in the human intestine - the small intestinal microbiota

The small intestinal microbiota has a crucial role in gastrointestinal health, affecting digestion, immune function, bile acid homeostasis and nutrient metabolism. The challenges of accessibility at this site mean that our knowledge of the small intestinal microbiota is less developed than of the colonic or faecal microbiota. Here, we summarize the features and fluctuations of the microbiota along the small intestinal tract, focusing on humans, and discuss physicochemical factors and assessment methods, including the technical challenges of investigating the low microbial biomass of the proximal small bowel. We highlight the essential protective mechanisms of the small intestine, including motility, the paracellular barrier and mucus, and secretory immunity, to show their roles in limiting excessive exposure of host tissues to microbial metabolites. We address current knowledge gaps, particularly the variability among individuals, the effects of dysbiosis of the small intestinal microbiota on health and how different taxa in small intestinal microbiota could compensate for each other functionally.

Inducible transposon mutagenesis for genome-scale forward genetics

Transposon insertion sequencing (Tn-seq) is a powerful method for genome-scale functional genetics in bacteria. However, its effectiveness is often limited by a lack of mutant diversity, caused by either inefficient transposon delivery or stochastic loss of mutants due to population bottlenecks. Here, we introduce "InducTn-seq", which leverages inducible mutagenesis for temporal control of transposition. InducTn-seq generates millions of transposon mutants from a single colony, enabling the sensitive detection of subtle fitness defects and transforming binary classifications of gene essentiality into a quantitative fitness measurement across both essential and non-essential genes. Using a mouse model of infectious colitis, we show that InducTn-seq bypasses a highly restrictive host bottleneck to generate a diverse transposon mutant population from the few cells that initiate infection, revealing the role of oxygen-related metabolic plasticity in pathogenesis. Overall, InducTn-seq overcomes the limitations of traditional Tn-seq, unlocking new possibilities for genome-scale forward genetic screens in bacteria.

Avian influenza and gut microbiome in poultry and humans: A "One Health" perspective

A gradual increase in avian influenza outbreaks has been found in recent years. It is highly possible to trigger the next human pandemic due to the characteristics of antigenic drift and antigenic shift in avian influenza virus (AIV). Although great improvements in understanding influenza viruses and the associated diseases have been unraveled, our knowledge of how these viruses impact the gut microbiome of both poultry and humans, as well as the underlying mechanisms, is still improving. The "One Health" approach shows better vitality in monitoring and mitigating the risk of avian influenza, which requires a multi-sectoral effort and highlights the interconnection of human health with environmental sustainability and animal health. Therefore, monitoring the gut microbiome may serve as a sentinel for protecting the common health of the environment, animals, and humans. This review summarizes the interactions between AIV infection and the gut microbiome of poultry and humans and their potential mechanisms. With the presented suggestions, we hope to address the current major challenges in the surveillance and prevention of microbiome-related avian influenza with the "One Health" approach.

Global knowledge mapping and emerging research trends in the microbiome and asthma: A bibliometric and visualized analysis using VOSviewer and CiteSpace

Background

Numerous prior studies have extensively highlighted the significance of the microbiome in association with asthma. While several studies have concentrated on the asthma microbiome in previous research, there is currently a lack of publications that employ bibliometric methods to assess this area.

Methods

In this study, the Web of Science Core Collection database was utilized as the data source, and the SCI-EXPANDED index was employed to ensure that the retrieved data were comprehensive and accurate. All original research articles and review articles related to the correlation between asthma and the microbiome were systematically searched from the inception of the database until June 20, 2023. These articles were subsequently visualized and analyzed using VOSviewer and CiteSpace software.

Results

A total of 1366 relevant publications were acquired, indicating a consistent annual increase in global publications in the field. The United States and China emerged as the top two contributors to international publications. Among prolific authors, Susan V. Lynch achieved the highest publication record, with Hans Bisgaard and Jakob Stokholm sharing the second position. The majority of publications concentrated on allergy-related and microbiome areas, with a few comprehensive journals standing out. Journals with 40 or more publications included the Journal of Allergy and Clinical Immunology, Allergy, Frontiers in Immunology, and PLOS One. The top 5 cited journals were the Journal of Allergy and Clinical Immunology, PLOS One, American Journal of Respiratory and Critical Care Medicine, Clinical and Experimental Allergy, and Nature. Upon analyzing keywords, high-frequency terms, such as asthma, gut microbiota, microbiome, children, childhood asthma, allergy, risk, exposure, inflammation, diversity, and chain fatty acids emerged as representative terms in the field.

Conclusion

This study systematically presented a comprehensive overview of the literature regarding the association between asthma and the microbiome over the last two decades. Through a bibliometric perspective, the findings may assist researchers with a better understanding of the essential information in the field.

The role of type II esophageal microbiota in achalasia: Activation of macrophages and degeneration of myenteric neurons

OBJECTIVE

The gut microbiota plays a critical role in the appropriate development and maintenance of the enteric nervous system (ENS). Esophageal achalasia (EA) is a rare motility disorder characterized by the selective degeneration of inhibitory neurons in the esophageal myenteric plexus. This study aimed to evaluate the composition of the esophageal microbiota in achalasia and explore the potential microbial mechanisms involved in its pathogenesis.

DESIGN

The lower esophageal mucosal microbiota was analyzed in patients with achalasia and control participants using 16 S rRNA sequencing. The association between the esophageal microbiota and achalasia was validated by inducing esophageal dysbiosis in C57BL/10 J and C57BL/10ScNJ (TLR4KO) mice via chronic exposure to ampicillin sodium in their drinking water.

RESULTS

The esophageal microbiota in EA patients had lower diversity and a predominance of Gram-negative bacteria (Type II microbiota) compared to that in the healthy controls. Additionally, the relative abundance of Rhodobacter decreased significantly in patients with achalasia, which correlated with an enrichment of lipopolysaccharide (LPS) biosynthesis based on the COG database. Antibiotic-treated mice showed an esophageal microbiota characterized by increased abundance of Gram-negative bacteria (Type II microbiome), decreased abundance of Rhodobacter, and enriched LPS biosynthesis. Compared to the control and TLR4KO mice, the antibiotic-treated wild-type mice had higher LES resting pressure, increased LES contraction rate after carbachol stimulation, and decreased relaxation response to L-arginine. Moreover, the number of myenteric neurons decreased, while the number of lamina propria macrophages (LpMs) increased after antibiotic exposure. Furthermore, the TLR4-MYD88-NF-κB pathway was up-regulated, and the production of TNF-α, IL-1β, and IL-6 increased in the antibiotic-treated mice.

CONCLUSIONS

Patients with achalasia exhibit esophageal dysbiosis, which may induce aberrant esophageal motility.

Decoding the role of gut microbiota in Alzheimer's pathogenesis and envisioning future therapeutic avenues

Alzheimer's disease (AD) emerges as a perturbing neurodegenerative malady, with a profound comprehension of its underlying pathogenic mechanisms continuing to evade our intellectual grasp. Within the intricate tapestry of human health and affliction, the enteric microbial consortium, ensconced within the milieu of the human gastrointestinal tract, assumes a role of cardinal significance. Recent epochs have borne witness to investigations that posit marked divergences in the composition of the gut microbiota between individuals grappling with AD and those favored by robust health. The composite vicissitudes in the configuration of the enteric microbial assembly are posited to choreograph a participatory role in the inception and progression of AD, facilitated by the intricate conduit acknowledged as the gut-brain axis. Notwithstanding, the precise nature of this interlaced relationship remains enshrouded within the recesses of obscurity, poised for an exhaustive revelation. This review embarks upon the endeavor to focalize meticulously upon the mechanistic sway exerted by the enteric microbiota upon AD, plunging profoundly into the execution of interventions that govern the milieu of enteric microorganisms. In doing so, it bestows relevance upon the therapeutic stratagems that form the bedrock of AD's management, all whilst casting a prospective gaze into the horizon of medical advancements.

Application of metagenomic sequencing of drainage fluid in rapid and accurate diagnosis of postoperative intra-abdominal infection: a diagnostic study

BACKGROUND

Postoperative intra-abdominal infection (PIAI) is one of the most serious complications of abdominal surgery, increasing the risk of postoperative morbidity and mortality and prolonging hospital stay. Rapid diagnosis of PIAI is of great clinical value. Unfortunately, the current diagnostic methods of PIAI are not fast and accurate enough.

METHODS

The authors performed an exploratory study to establish a rapid and accurate diagnostic method of PIAI. The authors explored the turnaround time and accuracy of metagenomic next-generation sequencing (mNGS) in diagnosing PIAI. Patients who underwent elective abdominal surgery and routine abdominal drainage with suspected PIAI were enroled in the study. The fresh midstream abdominal drainage fluid was collected for mNGS and culturing.

RESULTS

The authors found that the median sample-to-answer turnaround time of mNGS was dramatically decreased than that of culture-based methods (<24 h vs. 59.5-111 h). The detection coverage of mNGS was much broader than culture-based methods. The authors found 26 species from 15 genera could only be detected by mNGS. The accuracy of mNGS was not inferior to culture-based methods in the 8 most common pathogens detected from abdominal drainage fluid (sensitivity ranged from 75 to 100%, specificity ranged from 83.3 to 100%, and kappa values were higher than 0.5). Moreover, the composition of the microbial spectrum established by mNGS varied between upper and lower gastrointestinal surgery, enhancing the understanding of PIAI pathogenesis.

CONCLUSION

This study preliminarily revealed the clinical value of mNGS in the rapid diagnosis of PIAI and provided a rationale for further research.

Understanding the role of the gut microbiome in gastrointestinal cancer: A review

Gastrointestinal cancer represents one of the most diagnosed types of cancer. Cancer is a genetic and multifactorial disease, influenced by the host and environmental factors. It has been stated that 20% of cancer is caused by microorganisms such as Helicobacter pylori, hepatitis B and C virus, and human papillomavirus. In addition to these well-known microorganisms associated with cancer, it has been shown differences in the composition of the microbiota between healthy individuals and cancer patients. Some studies have suggested the existence of the selected microorganisms and their metabolites that can promote or inhibit tumorigenesis via some mechanisms. Recent findings have shown that gut microbiome and their metabolites can act as cancer promotors or inhibitors. It has been shown that gastrointestinal cancer can be caused by a dysregulation of the expression of non-coding RNA (ncRNA) through the gut microbiome. This review will summarize the latest reports regarding the relationship among gut microbiome, ncRNAs, and gastrointestinal cancer. The potential applications of diagnosing and cancer treatments will be discussed.

Analyzing the Complicated Connection Between Intestinal Microbiota and Cardiovascular Diseases

Relentless human curiosity to understand the basis of every aspect of medical science has led humanity to unlock the deepest secrets about the physiology of human existence and, in the process, has reached milestones that a century ago could only be imagined. Recent ground-breaking breakthroughs have helped scientists and physicians all over the world to update the scientific basis of diseases and hence further improve treatment outcomes. According to recent studies, scientists have found a link between intestinal flora and the pathogenesis of diseases, including cardiovascular diseases. Any change in the typical habitat of gut microbiota has been shown to result in the culmination of various metabolic and cardiac diseases. Therefore, gut microbiota can be credited for influencing the course of the development of a disease. Any change in the composition and function of bacterial species living in the gut can result in both beneficial and harmful effects on the body. Gut microbiota achieves this role by numerous mechanisms. Generations of various metabolites like TMAO (trimethylamine N-oxide), increased receptibility of various bacterial antigens, and disruption of the enzyme action in various metabolic pathways like the bile acids pathway may result in the development of metabolic as well as cardiovascular diseases. Even if they may not be the only etiological factor in the pathogenesis of a disease, they may very well serve as a contributing factor in worsening the outcome of the condition. Studies have shown that they actively play a role in the progression of cardiovascular diseases like atherosclerotic plaque formation and rising blood pressure. The focus of this review article is to establish a relation between various cardiovascular diseases and gut microbiota. This could prove beneficial for clinicians, health care providers, and scientists to develop novel therapeutic algorithms while treating cardiac patients.

Microbial community signatures for estimation of postmortem time intervals

The human body provides a complex ecosystem for symbiotic habitation of a huge number of microorganisms. These commensal microorganisms provide a huge benefit to the living host by acting against many deadly infections. Once the host dies, many changes in the complex ecosystem of the human body take place. The personalized microbes of a human body undergo successional change as many exogenous microbes attack the nutrient-rich cadaver after death. The succession pattern change of microbes in human cadaver allows postulating different models for estimation of Postmortem time interval (PMI). Estimation of PMI has a broad prospect from the criminal investigation point of view. Though many techniques are being used nowadays to estimate PMI, all of them have their pros and cons. With the advent of advanced molecular biological techniques, studies on the thanatomicrobiome of a human cadaver have gained pace and provide a superior alternative for conventional methods of PMI estimation. This chapter summarizes the recent advancements in the changes in signature microflora postmortem with change in human microenvironment to postulate a consensus model for estimation of PMI.

Isolation and sequencing of a single copy of an introgressed chromosome from a complex genome for gene and SNP identification

This manuscript describes the identification, isolation and sequencing of a single chromosome containing high value resistance genes from a complex polyploid where sequencing the whole genome is too costly. The large complex genomes of many crops constrain the use of new technologies for genome-assisted selection and genetic improvement. One method to simplify a genome is to break it into individual chromosomes by flow cytometry; however, in many crop species most chromosomes cannot be isolated individually. Flow sorting of a single copy of a chromosome has been developed in wheat, and here we demonstrate its use to identify markers of interest in an Erianthus/Sacchurum hybrid. Erianthus/Saccharum hybrids are of interest because Erianthus is known to be highly resistant to soil borne diseases which cause extensive sugarcane yield losses in Australia. Sugarcane (Saccharum) cultivars are autopolyploids with a highly complex genome and over 100 chromosomes. Flow cytometry for sugarcane, as in most crops, does not resolve individual chromosomes to a karyotype peak for sorting. To isolate a single chromosome, we used genomic in situ hybridization (GISH) to identify the flow karyotype region containing the Erianthus chromosomes, flow sorted single chromosomes from this region, PCR screened for the Erianthus chromosomes and sequenced them. One Erianthus chromosome amplified and sequenced well, and from this data we could identify 57 resistant type genes and SNPs in nearly half of these genes. We developed KASP SNP assays and demonstrated that the identified SNP markers segregated as expected in a small introgression population. The pipeline we developed here to flow sort and sequence single chromosomes could be used in any crop with a large complex genome to rapidly discover and develop markers to important loci.

New Insights into Stroke Prevention and Treatment: Gut Microbiome

Stroke, a lethal neurological disease, accounts for a grave economic burden on society. Despite extensive basic and clinical studies on stroke prevention, a precise effective treatment approach for stroke at this stage remains unavailable. The majority of our body's gut microbiota plays a vital role in food digestion, immune regulation, and nervous system development, which is highly associated with the development of some diseases. Multiple clinical studies have documented variation in the composition of gut microbiota between stroke patients and healthy counterparts. Moreover, the intervention of intestinal symbiotic microorganisms via several mechanisms plays an active role in stroke prognosis. In the prevention and treatment of stroke, the gut microbiota gives off a seductive glow, this is a promising therapeutic target. This paper summarizes the current knowledge of stroke and gut microbiota, and systematically describes the possible mechanisms of interaction between stroke and gut microbiota, the relationship between stroke-related risk factors and gut microbiota, and the treatment of gut flora using microorganisms. Thus, it could valuably elucidate the correlation of gut microbiota with stroke incidence, providing stroke researchers with a new strategy for stroke prevention and treatment by regulating gut microbiota.

Protective Immunity against Listeria monocytogenes in Rats, Provided by HCl- and NaOH-Induced Listeria monocytogenes Bacterial Ghosts (LMGs) as Vaccine Candidates

Listeria monocytogenes (Lm) bacterial ghosts (LMGs) were produced by the minimum inhibitory concentration (MIC) of HCl, H₂SO₄, and NaOH. Acid and alkali effects on the LMGs were compared by in vitro and in vivo analyses. Scanning electron microscope showed that all chemicals form lysis pores on the Lm cell envelopes. Real-time qPCR revealed a complete absence of genomic DNA in HCl- and H₂SO₄-induced LMGs but not in NaOH-induced LMGs. HCl-, H₂SO₄- and NaOH-induced LMGs showed weaker or missing protein bands on SDS-PAGE gel when compared to wild-type Lm. Murine macrophages exposed to the HCl-induced LMGs showed higher cell viability than those exposed to NaOH-induced LMGs or wild-type Lm. The maximum level of cytokine expression (TNF-α, iNOS, IFN-γ, and IL-10 mRNA) was observed in the macrophages exposed to NaOH-induced LMGs, while that of IL-1β mRNA was observed in the macrophages exposed to HCl-induced LMGs. To investigate LMGs as a vaccine candidate, mice were divided into PBS buffer-injected, HCl- and NaOH-induced LMGs immunized groups. Mice vaccinated with HCl- and NOH-induced LMGs, respectively, significantly increased in specific IgG antibodies, bactericidal activities of serum, and CD4⁺ and CD8⁺ T-cell population. Antigenic Lm proteins reacted with antisera against HCl- and NOH-induced LMGs, respectively. Bacterial loads in HCl- and NaOH-induced LMGs immunized mice were significantly lower than PBS-injected mice after virulent Lm challenges. It suggested that vaccination with LMGs induces both humoral and cell-mediated immune responses and protects against virulent challenges.

A randomized double-blind placebo controlled pilot study of probiotics in adolescents with severe obesity

PURPOSE

The purpose of the study is to assess the effect of probiotic supplementation on gut microbiota and insulin resistance in adolescents with severe obesity.

METHODS

Through a randomized, double blind, placebo-controlled, 12-week pilot clinical trial, 15 adolescents with severe obesity received either an oral probiotic 'Visbiome®' (n = 8) or placebo (n = 7). Anthropometry, fasting glucose, insulin, hs-CRP and stool for microbiome and calprotectin were collected at baseline (week 0) and 12 weeks after intervention.

RESULTS

Among completers (n = 4 in each of the two groups), mean change in fasting glucose was significantly lower in the probiotic group (0 ± 4 mg/dL) as compared to the placebo group (6.3 ± 1.7 mg/dL) (p = 0.028). Gut microbial Firmicutes to Bacteroidetes (F/B) ratio had a greater decline from week 0 to week 12 in the probiotic group (mean 17.7 ± 25.1 to 2.39 ± 2.0, respectively) but was not statistically significant (p = 0.06) as compared to in the placebo group (mean 12.8 ± 18.2 to 6.9 ± 5.61, respectively) (p = 0.89). Weight and BMI (mean ± SD) trended to remain stable in the treatment group (-1.07 ± 6.1 kg and -0.3 ± 2.2 kg/m2 respectively) as compared to the placebo group (3.9 ± 5.1 kg, 1.0 ± 1.6 kg/m2) but was not significant (p = 0.12 for weight and 0.38 for BMI). No significant change in the fasting insulin, HOMA-IR, or serum and stool inflammatory markers were noted between the two groups (p > 0.05). One participant in the treatment arm reported adverse effects of gastrointestinal intolerance.

CONCLUSION

Probiotic therapy with Visbiome® may improve the fasting glucose and possibly decrease the gut microbial F/B ratio as compared to placebo in adolescents with severe obesity. Future larger studies are required to confirm these findings.U.S. Clinical Trial Registry number: NCT03109587.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40200-021-00855-7.

Role of microbiota and related metabolites in gastrointestinal tract barrier function in NAFLD

The Gastrointestinal (GI) tract is composed of four main barriers: microbiological, chemical, physical and immunological. These barriers play important roles in maintaining GI tract homeostasis. In the crosstalk between these barriers, microbiota and related metabolites have been shown to influence GI tract barrier integrity, and alterations of the gut microbiome might lead to an increase in intestinal permeability. As a consequence, translocation of bacteria and their products into the circulatory system increases, reaching proximal and distal tissues, such as the liver. One of the most prevalent chronic liver diseases, Nonalcoholic Fatty Liver Disease (NAFLD), has been associated with an altered gut microbiota and barrier integrity. However, the causal link between them has not been fully elucidated yet. In this review, we aim to highlight relevant bacterial taxa and their related metabolites affecting the GI tract barriers in the context of NAFLD, discussing their implications in gut homeostasis and in disease.

Gastrointestinal Interaction between Dietary Amino Acids and Gut Microbiota: With Special Emphasis on Host Nutrition

The gastrointestinal tract (GIT) of humans and animals is host to a complex community of different microorganisms whose activities significantly influence host nutrition and health through enhanced metabolic capabilities, protection against pathogens, and regulation of the gastrointestinal development and immune system. New molecular technologies and concepts have revealed distinct interactions between the gut microbiota and dietary amino acids (AAs) especially in relation to AA metabolism and utilization in resident bacteria in the digestive tract, and these interactions may play significant roles in host nutrition and health as well as the efficiency of dietary AA supplementation. After the protein is digested and AAs and peptides are absorbed in the small intestine, significant levels of endogenous and exogenous nitrogenous compounds enter the large intestine through the ileocaecal junction. Once they move in the colonic lumen, these compounds are not markedly absorbed by the large intestinal mucosa, but undergo intense proteolysis by colonic microbiota leading to the release of peptides and AAs and result in the production of numerous bacterial metabolites such as ammonia, amines, short-chain fatty acids (SCFAs), branched-chain fatty acids (BCFAs), hydrogen sulfide, organic acids, and phenols. These metabolites influence various signaling pathways in epithelial cells, regulate the mucosal immune system in the host, and modulate gene expression of bacteria which results in the synthesis of enzymes associated with AA metabolism. This review aims to summarize the current literature relating to how the interactions between dietary amino acids and gut microbiota may promote host nutrition and health.

The Gastrointestinal Microbiota of the Common Marmoset (Callithrix jacchus)

The microbiota is heavily involved in both health and disease pathogenesis, but defining a normal, healthy microbiota in the common marmoset has been challenging. The aim of this review was to systematically review recent literature involving the gastrointestinal microbiome of common marmosets in health and disease. Twelve sources were included in this review. The gut microbiome composition was reviewed across institutions worldwide, and taxonomic shifts between healthy individuals were described. Unlike the human gut microbiome, which is dominated by Firmicutes and Bacteroidetes, the marmoset gut microbiome shows great plasticity across institutions, with 5 different phyla described as dominant in different healthy cohorts. Genera shared across institutions include Anaerobiospirillum, Bacteroides, Bifidobacterium, Collinsella, Fusobacterium, Megamonas, Megasphaera, Phascolarctobacterium, and Prevotella. Shifts in the abundance of Prevotella or Bifidobacterium or invasion by pathogens like Clostridium perfringens may be associated with disease. Changes in microbial composition have been described in healthy and diseased marmosets, but factors influencing the severe changes in microbial composition have not been established. Multi-institutional, prospective, and longitudinal studies that utilize multiple testing methodologies are required to determine sources of variability in the reporting of marmoset microbiomes. Furthermore, methods of microbial manipulation, whether by diet, enrichment, fecal microbiome transplantation, etc, need to be established to modulate and maintain robust and resilient microbiome communities in marmoset colonies and reduce the incidence of idiopathic gastrointestinal disease.

Resolving the Paradox of Colon Cancer Through the Integration of Genetics, Immunology, and the Microbiota

While colorectal cancers (CRC) are paradigmatic tumors invaded by effector memory lymphocytes, the mechanisms accounting for the relative resistance of MSI negative CRC to immunogenic cell death mediated by oxaliplatin and immune checkpoint inhibitors has remained an open conundrum. Here, we propose the viewpoint where its microenvironmental contexture could be explained -at least in part- by macroenvironmental cues constituted by the complex interplay between the epithelial barrier, its microbial ecosystem, and the local immune system. Taken together this dynamic ménage-à-trois offers novel coordinated actors of the humoral and cellular immune responses actionable to restore sensitivity to immune checkpoint inhibition. Solving this paradox involves breaking tolerance to crypt stem cells by inducing the immunogenic apoptosis of ileal cells in the context of an ileal microbiome shifted towards immunogenic bacteria using cytotoxicants. This manoeuver results in the elicitation of a productive Tfh and B cell dialogue in mesenteric lymph nodes culminating in tumor-specific memory CD8+ T cell responses sparing the normal epithelium.

Luminal microbiota related to Crohn's disease recurrence after surgery

BACKGROUND

Microbial factors are likely to be involved in the recurrence of Crohn's disease (CD) after bowel resection. We investigated the luminal microbiota before and longitudinally after surgery, in relation to disease recurrence, using 16S metagenomic techniques.

METHODS

In the prospective Post-Operative Crohn's Endoscopic Recurrence (POCER) study, fecal samples were obtained before surgery and 6, 12, and 18 months after surgery from 130 CD patients. Endoscopy was undertaken to detect disease recurrence, defined as Rutgeerts score ≥i2, at 6 months in two-thirds of patients and all patients at 18 months after surgery. The V2 region of the 16S rRNA gene was sequenced using Illumina MiSeq. Cluster analysis was performed at family level, assessing microbiome community differences between patients with and without recurrence.

RESULTS

Six microbial cluster groups were identified. The cluster associated with maintenance of remission was enriched for the Lachnospiraceae family [adjusted OR 0.47 (0.27-0.82), P = .007]. The OTU diversity of Lachnospiraceae within this cluster was significantly greater than in all other clusters. The cluster enriched for Enterobacteriaceae was associated with an increased risk of disease recurrence [adjusted OR 6.35 (1.24-32.44), P = .026]. OTU diversity of Enterobacteriaceae within this cluster was significantly greater than in other clusters.

CONCLUSIONS

Luminal bacterial communities are associated with protection from, and the occurrence of, Crohn's disease recurrence after surgery. Recurrence may relate to a higher abundance of facultatively anaerobic pathobionts from the Enterobacteriaceae family. The ecologic change of depleted Lachnospiraceae, a genus of butyrate-producing bacteria, may permit expansion of Enterobacteriaceae through luminal environmental perturbation.

An alternative pentose phosphate pathway in human gut bacteria for the degradation of C5 sugars in dietary fibers

The microbial degradation of pentoses in the human gut is a crucial factor for the utilization of plant-based dietary fibers. A vast majority of gut microbes are able to use these C5-sugars as a carbon and energy source. However, the underlying metabolic pathways are not fully understood. Bioinformatic analysis showed that a large number of abundant gut bacteria lack genes encoding a transaldolase as a key enzyme of the pentose phosphate pathway. Among them was the important human gut microbe Prevotella copri, which was able to grow in minimal media containing xylose or hemicelluloses as the sole carbon source. Therefore, we looked for an alternative pathway for pentose conversion in P. copri using bioinformatics, enzyme activity assays, and the detection of intermediates of pentose metabolism. It became evident that the organism converted C5-sugars via the sedoheptulose-1,7-bisphosphate pathway (SBPP) to connect pentose metabolism with glycolysis. To circumvent the transaldolase reaction, P. copri uses the combined catalysis of a pyrophosphate-dependent phosphofructokinase and a fructose-bisphosphate aldolase. Furthermore, we present strong evidence that the SBPP is widely distributed in important gut bacteria, including members of the phyla Bacteroides, Firmicutes, Proteobacteria, Verrucomicrobia, and Lentisphaerae.

The cultivable microbiota of the human distal ileum

OBJECTIVES

The existing literature on the microbiota of the ileum is inconsistent. To further characterize the microbiota, we analysed samples obtained directly from resected ileums used for urinary diversion after radical cystectomy.

METHODS

We included 150 patients with bladder cancer operated on from March 2016 to March 2019. Samples obtained by rubbing a swab against the ileal mucosa 25 cm from the ileocecal valve were cultivated at the local laboratory. Microbial colonies were identified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF).

RESULTS

The microbial density of the distal ileum was low. Among our samples, 79% (95% confidence interval (CI) 71%, 84%) harboured less than 1.6 × 10⁴ cfu/mL, whereas 36% (95% CI 28%, 44%) harboured less than 1.6 × 10³ cfu/mL. The flora was dominated by viridans streptococci, Candida, Actinomyces, Rothia and Lactobacillus species. Colon-related bacteria i.e. strict anaerobic bacteria, Enterobacteriales and enterococci, were recovered from 14% of the samples. Constipation was associated with increased recovery of colon-related bacteria. Antibiotic treatment prior to surgical procedures did not affect culture results. Increased age was significantly associated with more substantial fungal growth and use of proton pump inhibitors seemed to increase both bacterial and fungal growth.

CONCLUSIONS

The microbiota of the human distal ileum is sparse and differs significantly from the colonic microbiota both quantitatively and by composition. These findings contradict recent metagenomics studies based on samples collected by retrograde colonoscopy and emphasize the crucial importance of adequate sampling techniques.

Microbial communities in a dynamic in vitro model for the human ileum resemble the human ileal microbiota

The important role for the human small intestinal microbiota in health and disease has been widely acknowledged. However, the difficulties encountered in accessing the small intestine in a non-invasive way in healthy subjects have limited the possibilities to study its microbiota. In this study, a dynamic in vitro model that simulates the human ileum was developed, including its microbiota. Ileostomy effluent and fecal inocula were employed to cultivate microbial communities within the in vitro model. Microbial stability was repetitively achieved after 10 days of model operation with bacterial concentrations reaching on average 107 to 108 16S rRNA copy numbers/ml. High diversities similar to those observed in in vivo ileum samples were achieved at steady state using both fecal and ileostomy effluent inocula. Functional stability based on Short Chain Fatty Acid concentrations was reached after 10 days of operation using fecal inocula, but was not reached with ileostomy effluent as inoculum. Principal Components and cluster analysis of the phylogenetic profiles revealed that in vitro samples at steady state clustered closest to two samples obtained from the terminal ileum of healthy individuals, independent of the inoculum used, demonstrating that the in vitro microbiota at steady state resembles that of the human ileum.

Crohn's Disease Differentially Affects Region-Specific Composition and Aerotolerance Profiles of Mucosally Adherent Bacteria

BACKGROUND

The intestinal microbiota play a key role in the onset, progression, and recurrence of Crohn disease (CD). Most microbiome studies assay fecal material, which does not provide region-specific information on mucosally adherent bacteria that directly interact with host systems. Changes in luminal oxygen have been proposed as a contributor to CD dybiosis.

METHODS

The authors generated 16S rRNA data using colonic and ileal mucosal bacteria from patients with CD and without inflammatory bowel disease. We developed profiles reflecting bacterial abundance within defined aerotolerance categories. Bacterial diversity, composition, and aerotolerance profiles were compared across intestinal regions and disease phenotypes.

RESULTS

Bacterial diversity decreased in CD in both the ileum and the colon. Aerotolerance profiles significantly differed between intestinal segments in patients without inflammatory bowel disease, although both were dominated by obligate anaerobes, as expected. In CD, high relative levels of obligate anaerobes were maintained in the colon and increased in the ileum. Relative abundances of similar and distinct taxa were altered in colon and ileum. Notably, several obligate anaerobes, such as Bacteroides fragilis, dramatically increased in CD in one or both intestinal segments, although specific increasing taxa varied across patients. Increased abundance of taxa from the Proteobacteria phylum was found only in the ileum. Bacterial diversity was significantly reduced in resected tissues of patients who developed postoperative disease recurrence across 2 independent cohorts, with common lower abundance of bacteria from the Bacteroides, Streptococcus, and Blautia genera.

CONCLUSIONS

Mucosally adherent bacteria in the colon and ileum show distinct alterations in CD that provide additional insights not revealed in fecal material.

Distinct microbial and immune niches of the human colon

Gastrointestinal microbiota and immune cells interact closely and display regional specificity; however, little is known about how these communities differ with location. Here, we simultaneously assess microbiota and single immune cells across the healthy, adult human colon, with paired characterization of immune cells in the mesenteric lymph nodes, to delineate colonic immune niches at steady state. We describe distinct helper T cell activation and migration profiles along the colon and characterize the transcriptional adaptation trajectory of regulatory T cells between lymphoid tissue and colon. Finally, we show increasing B cell accumulation, clonal expansion and mutational frequency from the cecum to the sigmoid colon and link this to the increasing number of reactive bacterial species.

The Smallest Intestine (TSI)-a low volume in vitro model of the small intestine with increased throughput

There is a growing interest in understanding the fate and behaviour of probiotic microorganisms and bioactive compounds during passage of the human gastrointestinal tract (GIT). Here, we report the development of a small volume in vitro model called The smallest Intestine (TSI) with increased throughput focusing on simulating passage through the stomach and small intestine (SI). The basic TSI module consists of five reactors, with a working volume of 12 ml each. During the simulated passage through the SI, bile is absorbed and pH is adjusted to physiologically relevant values for duodenum, jejunum and ileum. A consortium of seven representative bacterial members of the ileum microbiota is included in the ileal stage of the model. The behaviour of three putative probiotic Lactobacillus strains during in vitro simulated upper GIT passage was tested in the model and results were compared to previous studies describing probiotic survival. It was found, that probiotic persistence is strongly related to whether food was ingested, but also to presence of the ileal microbiota, which significantly impacted probiotic survival. In conclusion, TSI allows testing a substantial number of samples, at low cost and short time, and is thus suitable as an in vitro screening platform.

Review article: emerging role of the gut microbiome in the progression of nonalcoholic fatty liver disease and potential therapeutic implications

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a prevalent disorder associated with obesity and diabetes. Few treatment options are effective for patients with NAFLD, but connections between the gut microbiome and NAFLD and NAFLD-associated conditions suggest that modulation of the gut microbiota could be a novel therapeutic option.

AIM

To examine the effect of the gut microbiota on pathophysiologic causes of NAFLD and assess the potential of microbiota-targeting therapies for NAFLD.

METHODS

A PubMed search of the literature was performed; relevant articles were included.

RESULTS

The composition of bacteria in the gastrointestinal tract can enhance fat deposition, modulate energy metabolism and alter inflammatory processes. Emerging evidence suggests a role for the gut microbiome in obesity and metabolic syndrome. NAFLD is often considered the hepatic manifestation of metabolic syndrome, and there has been tremendous progress in understanding the association of gut microbiome composition with NAFLD disease severity. We discuss the role of the gut microbiome in NAFLD pathophysiology and whether the microbiome composition can differentiate the two categories of NAFLD: nonalcoholic fatty liver (NAFL, the non-progressive form) vs nonalcoholic steatohepatitis (NASH, the progressive form). The association between gut microbiome and fibrosis progression in NAFLD is also discussed. Finally, we review whether modulation of the gut microbiome plays a role in improving treatment outcomes for patients with NAFLD.

CONCLUSIONS

Multiple pathophysiologic pathways connect the gut microbiome with the pathophysiology of NAFLD. Therefore, therapeutics that effectively target the gut microbiome may be beneficial for the treatment of patients with NAFLD.

Spatial and Temporal Analysis of the Stomach and Small-Intestinal Microbiota in Fasted Healthy Humans

Although the microbiota in the proximal gastrointestinal (GI) tract have been implicated in health and disease, much about these microbes remains understudied compared to those in the distal GI tract. This study characterized the microbiota across multiple proximal GI sites over time in healthy individuals. As part of a study of the pharmacokinetics of oral mesalamine administration, healthy, fasted volunteers (n = 8; 10 observation periods total) were orally intubated with a four-lumen catheter with multiple aspiration ports. Samples were taken from stomach, duodenal, and multiple jejunal sites, sampling hourly (≤7 h) to measure mesalamine (administered at t = 0), pH, and 16S rRNA gene-based composition. We observed a predominance of Firmicutes across proximal GI sites, with significant variation compared to stool. The microbiota was more similar within individuals over time than between subjects, with the fecal microbiota being unique from that of the small intestine. The stomach and duodenal microbiota displayed highest intraindividual variability compared to jejunal sites, which were more stable across time. We observed significant correlations in the duodenal microbial composition with changes in pH; linear mixed models identified positive correlations with multiple Streptococcus operational taxonomic units (OTUs) and negative correlations with multiple Prevotella and Pasteurellaceae OTUs. Few OTUs correlated with mesalamine concentration. The stomach and duodenal microbiota exhibited greater compositional dynamics than the jejunum. Short-term fluctuations in the duodenal microbiota were correlated with pH. Given the unique characteristics and dynamics of the proximal GI tract microbiota, it is important to consider these local environments in health and disease states.IMPORTANCE The gut microbiota are linked to a variety of gastrointestinal diseases, including inflammatory bowel disease. Despite this importance, microbiota dynamics in the upper gastrointestinal tract are understudied. Our article seeks to understand what factors impact microbiota dynamics in the healthy human upper gut. We found that the upper gastrointestinal tract contains consistently prevalent bacterial OTUs that dominate the overall community. Microbiota variability is highest in the stomach and duodenum and correlates with pH.

Identification and Analysis of Human Microbe-Disease Associations by Matrix Decomposition and Label Propagation

Studies have shown that microbes exist widely in the human body and are closely related to human complex diseases. Predicting potential associations between microbes and diseases is conducive to understanding the mechanisms of complex diseases and can also facilitate the diagnosis and prevention of human diseases. In this paper, we put forward the Matrix Decomposition and Label Propagation for Human Microbe-Disease Association prediction (MDLPHMDA) on the basis of the dataset of known microbe-disease associations collected from the database of HMDAD and the Gaussian interaction profile kernel similarity for diseases and microbes, disease symptom similarity. Moreover, the performance of our model was evaluated by means of leave-one-out cross validation and five-fold cross validation, and the corresponding AUCs of 0.9034 and 0.8954 ± 0.0030 were gained, respectively. In case studies, 10, 9, 9, and 8 out of the top 10 predicted microbes for asthma, colorectal carcinoma, liver cirrhosis, and type 1 diabetes were confirmed by literatures, respectively. Overall, evaluation results showed that MDLPHMDA has good performance in potential microbe-diseasepositive free parameter, which associations prediction.

Effects of synbiotics on ileal microbiota

Background & objectives:

Despite advancements in molecular-based methods, the composition of the human ileal microbiota and the effects of synbiotics/probiotics on its microbes remain poorly understood. The aim of this study was to determine the composition of the mucus microbiota in the human ileum and to assess the effects of oral administration of synbiotics on the microbiota.

Methods:

As part of a clinical trial for synbiotics treatment and surgical infection, ileal mucus was sampled when resection of the ileocecal portion was required. The microbiota composition was examined using 16S rRNA-targeted real-time-quantitative polymerase chain reaction.

Results:

A total of 33 samples from the synbiotics group and 39 from the control group were analyzed. Total numbers of bacteria in the ileum were 10^8.5 cells/g in the synbiotics group and 10^8.4 cells/g in the control group, in which obligate anaerobes were dominant over facultative anaerobes. The level of Enterobacteriaceae was significantly lower in the synbiotics group than in the control group. The administered probiotics species Lactobacillus casei strain Shirota and Bifidobacterium breve strain Yakult were detected in 42 and 76 per cent of the synbiotics group, respectively. No significant correlations were observed between tumour stage/size and the various microbes present, except for a negative correlation between tumour size and Bifidobacterium.

Interpretation & conclusions:

The present analysis of a substantial number of samples from surgically resected intestines showed an abundance of obligate anaerobes as a characteristic feature of the ileal mucus microbiota. Our results also indicated that the synbiotics intervention induced a prominent reduction in Enterobacteriaceae in the ileal microbiota.

Update on the Gastrointestinal Microbiome in Systemic Sclerosis

PURPOSE OF REVIEW

Accumulating evidence suggests that gut microbiota affect the development and function of the immune system and may play a role in the pathogenesis of autoimmune diseases. The purpose of this review is to summarize recent studies reporting gastrointestinal microbiota aberrations associated with the systemic sclerosis disease state.

RECENT FINDINGS

The studies described herein have identified common changes in gut microbial composition. Specifically, patients with SSc have decreased abundance of beneficial commensal genera (e.g., Faecalibacterium, Clostridium, and Bacteroides) and increased abundance of pathobiont genera (e.g., Fusobacterium, Prevotella, Erwinia). In addition, some studies have linked specific genera with the severity of gastrointestinal symptoms in systemic sclerosis. More research is needed to further characterize the gastrointestinal microbiota in systemic sclerosis and understand how microbiota perturbations can affect inflammation, fibrosis, and clinical outcomes. Interventional studies aimed at addressing/correcting these perturbations, either through dietary modification, pro/pre-biotic supplementation, or fecal transplantation, may lead to improved outcomes for patients with systemic sclerosis.

Microbial Ecology along the Gastrointestinal Tract

The ecosystem of the human gastrointestinal (GI) tract traverses a number of environmental, chemical, and physical conditions because it runs from the oral cavity to the anus. These differences in conditions along with food or other ingested substrates affect the composition and density of the microbiota as well as their functional roles by selecting those that are the most suitable for that environment. Previous studies have mostly focused on Bacteria, with the number of studies conducted on Archaea, Eukarya, and Viruses being limited despite their important roles in this ecosystem. Furthermore, due to the challenges associated with collecting samples directly from the inside of humans, many studies are still exploratory, with a primary focus on the composition of microbiomes. Thus, mechanistic studies to investigate functions are conducted using animal models. However, differences in physiology and microbiomes need to be clarified in order to aid in the translation of animal model findings into the context of humans. This review will highlight Bacteria, Archaea, Fungi, and Viruses, discuss differences along the GI tract of healthy humans, and perform comparisons with three common animal models: rats, mice, and pigs.

The gastrointestinal microbiota and its role in oncogenesis

Advances in research techniques have made it possible to map the microbial communities in the gastrointestinal (GI) tract, where the majority of bacteria in the human body reside. Disturbances in these communities are referred to as dysbiosis and have been associated with GI cancers. Although dysbiosis is observed in several GI malignancies, the specific role of these changes has not been understood to the extent of Helicobacter pylori (HP) in gastric cancer (GC). This review will address the bacterial communities along the GI tract, from the oral cavity to the anal canal, particularly focusing on bacterial dysbiosis and carcinogenesis. Just as non-HP bacteria in the stomach may interact with HP in gastric carcinogenesis, the same may hold true for other GI tract malignancies, where an interplay between microbes in carcinogenesis seems conceivable, especially in colorectal cancer (CRC). In the last part of this review we will discuss the potential mechanisms of bacterial dysbiosis in GI carcinogenesis.

A review of metabolic potential of human gut microbiome in human nutrition

The human gut contains a plethora of microbes, providing a platform for metabolic interaction between the host and microbiota. Metabolites produced by the gut microbiota act as a link between gut microbiota and its host. These metabolites act as messengers having the capacity to alter the gut microbiota. Recent advances in the characterization of the gut microbiota and its symbiotic relationship with the host have provided a platform to decode metabolic interactions. The human gut microbiota, a crucial component for dietary metabolism, is shaped by the genetic, epigenetic and dietary factors. The metabolic potential of gut microbiota explains its significance in host health and diseases. The knowledge of interactions between microbiota and host metabolism, as well as modification of microbial ecology, is really beneficial to have effective therapeutic treatments for many diet-related diseases in near future. This review cumulates the information to map the role of human gut microbiota in dietary component metabolism, the role of gut microbes derived metabolites in human health and host-microbe metabolic interactions in health and diseases.

Investigation and characterization of β-lactam resistance in Escherichia coli strains isolated from bamboo rats (Rhizomys sinensis) in Zhejiang province, China

This study was undertaken to investigate drug resistance in Escherichia coli (E. coli) strains isolated from bamboo rats in Zhejiang province of China. One hundred and fifty-four E. coli strains were isolated from dead bamboo rats. Polymerase chain reaction (PCR) was used to detect the representative genes encoding resistance to commonly used β-lactam antibiotics. Highest resistance was observed for cefradine (24.03%), followed by penicillin (20.78%) and ceftazidime (20.13%). The isolation rates of β-lactam resistance genes were 53.25, 48.70, 15.58 and 14.29% for bla _TEM, bla _CTX-M, bla _OXA and bla _SHV, respectively, while 62 (40.26%) E. coli isolates harbored multiple β-lactam resistance genes. These results also suggested that long term use of these antibiotics leads to antibimicrobial resistance. We believe that this study will provide a guideline for veterinarians and a research basis for examining resistance-encoding genes in other food animals like bamboo rats.

Human Gut Microbiota: Toward an Ecology of Disease

Composed of trillions of individual microbes, the human gut microbiota has adapted to the uniquely diverse environments found in the human intestine. Quickly responding to the variances in the ingested food, the microbiota interacts with the host via reciprocal biochemical signaling to coordinate the exchange of nutrients and proper immune function. Host and microbiota function as a unit which guards its balance against invasion by potential pathogens and which undergoes natural selection. Disturbance of the microbiota composition, or dysbiosis, is often associated with human disease, indicating that, while there seems to be no unique optimal composition of the gut microbiota, a balanced community is crucial for human health. Emerging knowledge of the ecology of the microbiota-host synergy will have an impact on how we implement antibiotic treatment in therapeutics and prophylaxis and how we will consider alternative strategies of global remodeling of the microbiota such as fecal transplants. Here we examine the microbiota-human host relationship from the perspective of the microbial community dynamics.

Metabolic Profiling Reveals Differences in Plasma Concentrations of Arabinose and Xylose after Consumption of Fiber-Rich Pasta and Wheat Bread with Differential Rates of Systemic Appearance of Exogenous Glucose in Healthy Men

BACKGROUND

The consumption of products rich in cereal fiber and with a low glycemic index is implicated in a lower risk of metabolic diseases. Previously, we showed that the consumption of fiber-rich pasta compared with bread resulted in a lower rate of appearance of exogenous glucose and a lower glucose clearance rate quantified with a dual-isotope technique, which was in accordance with a lower insulin and glucose-dependent insulinotropic polypeptide response.

OBJECTIVE

To gain more insight into the acute metabolic consequences of the consumption of products resulting in differential glucose kinetics, postprandial metabolic profiles were determined.

METHODS

In a crossover study, 9 healthy men [mean ± SEM age: 21 ± 0.5 y; mean ± SEM body mass index (kg/m²): 22 ± 0.5] consumed wheat bread (132 g) and fresh pasta (119 g uncooked) enriched with wheat bran (10%) meals. A total of 134 different metabolites in postprandial plasma samples (at -5, 30, 60, 90, 120, and 180 min) were quantified by using a gas chromatography-mass spectrometry-based metabolomics approach (secondary outcomes). Two-factor ANOVA and advanced multivariate statistical analysis (partial least squares) were applied to detect differences between both food products.

RESULTS

Forty-two different postprandial metabolite profiles were identified, primarily representing pathways related to protein and energy metabolism, which were on average 8% and 7% lower after the men consumed pasta rather than bread, whereas concentrations of arabinose and xylose were 58% and 53% higher, respectively. Arabinose and xylose are derived from arabinoxylans, which are important components of wheat bran. The higher bioavailability of arabinose and xylose after pasta intake coincided with a lower rate of appearance of glucose and amino acids. We speculate that this higher bioavailability is due to higher degradation of arabinoxylans by small intestinal microbiota, facilitated by the higher viscosity of arabinoxylans after pasta intake than after bread intake.

CONCLUSION

This study suggests that wheat bran, depending on the method of processing, can increase the viscosity of the meal bolus in the small intestine and interfere with macronutrient absorption in healthy men, thereby influencing postprandial glucose and insulin responses. This trial was registered at www.controlled-trials.com as ISRCTN42106325.

Dynamic changes of yak (Bos grunniens) gut microbiota during growth revealed by polymerase chain reaction-denaturing gradient gel electrophoresis and metagenomics

OBJECTIVE

To understand the dynamic structure, function, and influence on nutrient metabolism in hosts, it was crucial to assess the genetic potential of gut microbial community in yaks of different ages.

METHODS

The denaturing gradient gel electrophoresis (DGGE) profiles and Illumina-based metagenomic sequencing on colon contents of 15 semi-domestic yaks were investigated. Unweighted pairwise grouping method with mathematical averages (UPGMA) clustering and principal component analysis (PCA) were used to analyze the DGGE fingerprint. The Illumina sequences were assembled, predicted to genes and functionally annotated, and then classified by querying protein sequences of the genes against the Kyoto encyclopedia of genes and genomes (KEGG) database.

RESULTS

Metagenomic sequencing showed that more than 85% of ribosomal RNA (rRNA) gene sequences belonged to the phylum Firmicutes and Bacteroidetes, indicating that the family Ruminococcaceae (46.5%), Rikenellaceae (11.3%), Lachnospiraceae (10.0%), and Bacteroidaceae (6.3%) were dominant gut microbes. Over 50% of non-rRNA gene sequences represented the metabolic pathways of amino acids (14.4%), proteins (12.3%), sugars (11.9%), nucleotides (6.8%), lipids (1.7%), xenobiotics (1.4%), coenzymes, and vitamins (3.6%). Gene functional classification showed that most of enzyme-coding genes were related to cellulose digestion and amino acids metabolic pathways.

CONCLUSION

Yaks' age had a substantial effect on gut microbial composition. Comparative metagenomics of gut microbiota in 0.5-, 1.5-, and 2.5-year-old yaks revealed that the abundance of the class Clostridia, Bacteroidia, and Lentisphaeria, as well as the phylum Firmicutes, Bacteroidetes, Lentisphaerae, Tenericutes, and Cyanobacteria, varied more greatly during yaks' growth, especially in young animals (0.5 and 1.5 years old). Gut microbes, including Bacteroides, Clostridium, and Lentisphaeria, make a contribution to the energy metabolism and synthesis of amino acid, which are essential to the normal growth of yaks.

A fibrolytic potential in the human ileum mucosal microbiota revealed by functional metagenomic

The digestion of dietary fibers is a major function of the human intestinal microbiota. So far this function has been attributed to the microorganisms inhabiting the colon, and many studies have focused on this distal part of the gastrointestinal tract using easily accessible fecal material. However, microbial fermentations, supported by the presence of short-chain fatty acids, are suspected to occur in the upper small intestine, particularly in the ileum. Using a fosmid library from the human ileal mucosa, we screened 20,000 clones for their activities against carboxymethylcellulose and xylans chosen as models of the major plant cell wall (PCW) polysaccharides from dietary fibres. Eleven positive clones revealed a broad range of CAZyme encoding genes from Bacteroides and Clostridiales species, as well as Polysaccharide Utilization Loci (PULs). The functional glycoside hydrolase genes were identified, and oligosaccharide break-down products examined from different polysaccharides including mixed-linkage β-glucans. CAZymes and PULs were also examined for their prevalence in human gut microbiome. Several clusters of genes of low prevalence in fecal microbiome suggested they belong to unidentified strains rather specifically established upstream the colon, in the ileum. Thus, the ileal mucosa-associated microbiota encompasses the enzymatic potential for PCW polysaccharide degradation in the small intestine.

Survival and Metabolic Activity of Pediocin Producer Pediococcus acidilactici UL5: Its Impact on Intestinal Microbiota and Listeria monocytogenes in a Model of the Human Terminal Ileum

Pediococcus acidilactici UL5 is a promising probiotic candidate due to its high survival rate under gastric and duodenal conditions and to its ability to produce the antilisterial bacteriocin pediocin PA-1. Its survival, metabolic activity, and impact on Listeria monocytogenes in a continuous stirred tank reactor containing immobilized human intestinal microbiota were studied over a period of 32 days of feeding a nutrient medium simulating ileal chyme. The impact of P. acidilactici UL5 on different bacterial groups of intestinal origin as well as its survival and its impact on L. monocytogenes were quantified using quantitative polymerase chain reaction coupling with propidium monoazide (PMA-qPCR), which was shown to detect and quantify viable bacteria only. P. acidilactici UL5 and its non-pediocin-producing mutant had no effect on the microbiota, but the producing strain induced an increase in the production of acetic and propionic acids. P. acidilactici survived but appeared to be a poor competitor with intestinal microbiota, dropping by 1.3 and 2.8 log₁₀ after 8 h of fermentation to 10⁴ colony-forming units (cfu) mL^-1. A 1.64 log but non-significant reduction of Listeria was observed when P. acidilactici UL5 was added at 10⁸ cfu mL^-1. P. acidilactici UL5 isolated from the reactor after 3 days was still able to produce the active bacteriocin. These data demonstrate that P. acidilactici UL5 is capable of surviving transit through the ileum without losing its ability to produce pediocin PA-1 but seems to not be enough competitive with the great diversity of organisms found in the ileum.

PCR Conditions for 16S Primers for Analysis of Microbes in the Colon of Rats

The study of the composition of the intestinal flora is important to the health of the host, playing a key role in maintaining intestinal homeostasis and the evolution of the immune system. For these studies, various universal primers of the 16S rDNA gene are used in microbial taxonomy. Here, we report an evaluation of 5 universal primers to explore the presence of microbial DNA in colon biopsies preserved in RNAlater solution. The DNA extracted was used for the amplification of PCR products containing the variable (V) regions of the microbial 16S rDNA gene. The PCR products were studied by restriction fragment length polymorphism (RFLP) analysis and DNA sequence, whose percent of homology with microbial sequences reported in GenBank was verified using bioinformatics tools. The presence of microbes in the colon of rats was quantified by the quantitative PCR (qPCR) technique. We obtained microbial DNA from rat, useful for PCR analysis with the universal primers for the bacteria 16S rDNA. The sequences of PCR products obtained from a colon biopsy of the animal showed homology with the classes bacilli (Lactobacillus spp) and proteobacteria, normally represented in the colon of rats. The proposed methodology allowed the attainment of DNA of bacteria with the quality and integrity for use in qPCR, sequencing, and PCR-RFLP analysis. The selected universal primers provided knowledge of the abundance of microorganisms and the formation of a preliminary test of bacterial diversity in rat colon biopsies.

[Characterization, influence and manipulation of the gastrointestinal microbiota in health and disease]

The gastrointestinal tract harbors trillions of microorganisms that are indispensable for health. The gastrointestinal microbiota can be studied using culture and molecular methods. The applications of massive sequencing are constantly increasing, due to their high yield, increasingly accessible costs, and the availability of free software for data analysis. The present article provides a detailed review of a large number of studies on the gastrointestinal microbiota and its influence on human health; particular emphasis is placed on the evidence suggesting a relationship between the gastrointestinal microbial ecosystem and diverse physiological and immune/inflammatory processes. Discussion of the articles analyzed combines a medical approach and current concepts of microbial molecular ecology. The present revision aims to be useful to those interested in the gastrointestinal microbiota and its possible alteration to maintain, re-establish and enhance health in the human host.

Characterization of the rumen microbiome of Indian Kankrej cattle (Bos indicus) adapted to different forage diet

Present study described rumen microbiome of Indian cattle (Kankrej breed) to better understand the microbial diversity and largely unknown functional capacity of the rumen microbiome under different dietary treatments. Kankrej cattle were gradually adapted to a high-forage diet (four animals with dry forage and four with green forage) containing 50 % (K1), 75 % (K2) to 100 % (K3) forage, and remaining concentrate diet, each for 6 weeks followed by analysis of rumen fiber adherent and fiber-free metagenomic community by shotgun sequencing using ion torrent PGM platform and EBI-metagenomics annotation pipeline. Taxonomic analysis indicated that rumen microbiome was dominated by Bacteroidetes followed by Firmicutes, Fibrobacter, Proteobacteria, and Tenericutes. Functional analysis based on gene ontology classified all reads in total 157 categories based on their functional role in biological, molecular, and cellular component with abundance of genes associated with hydrolase activity, membrane, transport, transferase, and different metabolism (such as carbohydrate and protein). Statistical analysis using STAMP revealed significant differences (P < 0.05) between solid and liquid fraction of rumen (in 65 categories), between all three treatments (in 56 categories), and between green and dry roughage (17 categories). Diet treatment also exerted significant difference in environmental gene tags (EGTs) involved in metabolic pathways for production of volatile fatty acids. EGTs for butyrate production were abundant in K2, whereas EGTs for propionate production was abundant during K1. Principal component analysis also demonstrated that diet proportion, fraction of rumen, and type of forage affected rumen microbiome at taxonomic as well as functional level.

Fecal microbiome analysis as a diagnostic test for diverticulitis

Disease-specific variations in intestinal microbiome composition have been found for a number of intestinal disorders, but little is known about diverticulitis. The purpose of this study was to compare the fecal microbiota of diverticulitis patients with control subjects from a general gastroenterological practice and to investigate the feasibility of predictive diagnostics based on complex microbiota data. Thirty-one patients with computed tomography (CT)-proven left-sided uncomplicated acute diverticulitis were included and compared with 25 control subjects evaluated for a range of gastrointestinal indications. A high-throughput polymerase chain reaction (PCR)-based profiling technique (IS-pro) was performed on DNA isolates from baseline fecal samples. Differences in bacterial phylum abundance and diversity (Shannon index) of the resulting profiles were assessed by conventional statistics. Dissimilarity in microbiome composition was analyzed with principal coordinate analysis (PCoA) based on cosine distance measures. To develop a prediction model for the diagnosis of diverticulitis, we used cross-validated partial least squares discriminant analysis (PLS-DA). Firmicutes/Bacteroidetes ratios and Proteobacteria load were comparable among patients and controls (p = 0.20). The Shannon index indicated a higher diversity in diverticulitis for Proteobacteria (p < 0.00002) and all phyla combined (p = 0.002). PCoA based on Proteobacteria profiles resulted in visually separate clusters of patients and controls. The diagnostic accuracy of the cross-validated PLS-DA regression model was 84 %. The most discriminative species derived largely from the family Enterobacteriaceae. Diverticulitis patients have a higher diversity of fecal microbiota than controls from a mixed population, with the phylum Proteobacteria defining the difference. The analysis of intestinal microbiota offers a novel way to diagnose diverticulitis.

Investigation of antimicrobial resistance in Escherichia coli and enterococci isolated from Tibetan pigs

Objectives

This study investigated the antimicrobial resistance of Escherichia coli and enterococci isolated from free-ranging Tibetan pigs in Tibet, China, and analyzed the influence of free-ranging husbandry on antimicrobial resistance.

Methods

A total of 232 fecal samples were collected from Tibetan pigs, and the disk diffusion method was used to examine their antimicrobial resistance. Broth microdilution and agar dilution methods were used to determine minimum inhibitory concentrations for antimicrobial agents for which disks were not commercially available.

Results

A total of 129 E. coli isolates and 84 Enterococcus isolates were recovered from the fecal samples. All E. coli isolates were susceptible to amoxicillin/clavulanic acid, and 40.4% were resistant to tetracycline. A small number of isolates were resistant to florfenicol (27.9%), ampicillin (27.9%), sulfamethoxazole/trimethoprim (19.4%), nalidixic acid (19.4%), streptomycin (16.2%) and ceftiofur (10.9%), and very low resistance rates to ciprofloxacin (7.8%), gentamicin (6.9%), and spectinomycin (2.3%) were observed in E. coli. All Enterococcus isolates, including E. faecium, E. faecalis, E. hirae, and E. mundtii, were susceptible to amoxicillin/clavulanic acid and vancomycin, but showed high frequencies of resistance to oxacillin (92.8%), clindamycin (82.1%), tetracycline (64.3%), and erythromycin (48.8%). Resistance rates to florfenicol (17.9%), penicillin (6.0%), ciprofloxacin (3.6%), levofloxacin (1.2%), and ampicillin (1.2%) were low. Only one high-level streptomycin resistant E. faecium isolate and one high-level gentamicin resistant E. faecium isolate were observed. Approximately 20% and 70% of E. coli and Enterococcus isolates, respectively, were defined as multidrug-resistant.

Conclusions

In this study, E. coli and Enterococcus isolated from free-ranging Tibetan pigs showed relatively lower resistance rates than those in other areas of China, where more intensive farming practices are used. These results also revealed that free-range husbandry and absence of antibiotic use could decrease the occurrence of antimicrobial resistance to some extent.

Changes in bacterial population of gastrointestinal tract of weaned pigs fed with different additives

This study aimed to provide novel insights into the gastrointestinal microbial diversity from different gastrointestinal locations in weaning piglets using PCR-restriction fragment length polymorphism (PCR-RFLP). Additionally, the effect of different feed additives was analyzed. Thirty-two piglets were fed with four different diets: a control group and three enriched diets, with avilamycin, sodium butyrate, and a plant extract mixture. Digesta samples were collected from eight different gastrointestinal segments of each animal and the bacterial population was analysed by a PCR-RFLP technique that uses 16S rDNA gene sequences. Bacterial diversity was assessed by calculating the number of bands and the Shannon-Weaver index. Dendrograms were constructed to estimate the similarity of bacterial populations. A higher bacterial diversity was detected in large intestine compared to small intestine. Among diets, the most relevant microbial diversity differences were found between sodium butyrate and plant extract mixture. Proximal jejunum, ileum, and proximal colon were identified as those segments that could be representative of microbial diversity in pig gut. Results indicate that PCR-RFLP technique allowed detecting modifications on the gastrointestinal microbial ecology in pigs fed with different additives, such as increased biodiversity by sodium butyrate in feed.