Explore the vast range of titles available.

One sentence summary: The review summarises the state of the art for studying gut microbes-mucus interactions using in vitro, ex vivo and in vivo experimental models. Editor: Ehud Banin † These authors contributed equally to this work ABSTRACT A close symbiotic relationship exists between the intestinal microbiota and its host. A critical component of gut homeostasis is the presence of a mucus layer covering the gastrointestinal tract. Mucus is a viscoelastic gel at the interface between the luminal content and the host tissue that provides a habitat to the gut microbiota and protects the intestinal epithelium. The review starts by setting up the biological context underpinning the need for experimental models to study gut bacteria-mucus interactions in the digestive environment. We provide an overview of the structure and function of intestinal mucus and mucins, their interactions with intestinal bacteria (including commensal, probiotics and pathogenic microorganisms) and their role in modulating health and disease states. We then describe the characteristics and potentials of experimental models currently available to study the mechanisms underpinning the interaction of mucus with gut microbes, including in vitro, ex vivo and in vivo models. We then discuss the limitations and challenges facing this field of research.

In order to investigate the effect and appropriate dose of prebiotics, this study evaluated the effect of two levels of xylooligosaccharides (XOS) in cats. Twenty-four healthy adult cats were divided into three groups: no-XOS control diet with 1% cellulose; low XOS supplementation (LXOS) with 0.04% XOS and 0.96% cellulose; and high XOS supplementation (HXOS) with 0.40% XOS and 0.60% cellulose. Both XOS groups increased blood 3-hydroxybutyryl carnitine levels and decreased hexadecanedioyl carnitine levels. Both XOS treatments displayed an increased bacterial abundance of Blautia, Clostridium XI, and Collinsella and a decreased abundance of Megasphaera and Bifidobacterium. LXOS groups increased fecal pH and bacterial abundance of Streptococcus and Lactobacillus, decreased blood glutaryl carnitine concentration, and Catenibacterium abundance. HXOS group showed a more distinct microbiome profile and higher species richness, and an increased bacterial abundance of Subdoligranulum, Ruminococcaceae genus (unassigned genus), Erysipelotrichaceae genus, and Lachnospiraceae. Correlations between bacterial abundances and blood and fecal parameters were also observed. In conclusion, XOS could benefit feline gut health by altering microbiota; its effects dependant on the dose. The higher-dose XOS increased bacterial populations that possibly promoted intestinal fermentation, while the lower dose altered populations of carbohydrate-metabolic microbiota and possibly modulated host metabolism. Low-dose prebiotics may become a trend in future studies.

Abstract Growing evidence suggests the importance of the small intestinal bacteria in the diet-host-microbiota dialogue in various facets of health and disease. Yet, this body site is still poorly explored and its ecology and mechanisms of interaction with the host are just starting to be unraveled. In this review, we describe the current knowledge on the small intestinal ecology, its composition and diversity, and how the intestinal bacteria in homeostatic conditions participate in nutrient digestion and absorption. We illustrate the importance of a controlled bacterial density and of the preservation of absorptive surface for the host's nutritional status. In particular, we discuss these aspects of the small intestinal environment in the framework of two disease conditions, namely small intestinal bacterial overgrowth (SIBO) and short bowel syndrome (SBS). We also detail in vivo, ex vivo and in vitro models developed to simulate the small intestinal environment, some applied for (diet-)host-bacteria interaction studies. Lastly, we highlight recent technological, medical and scientific advances applicable to investigate this complex and yet understudied body environment to broaden our knowledge in support of further progress in the medical practice, and to proceed towards the integration of the (small)intestinal bacteria in personalized therapeutic approaches.

Background. It is widely assumed that the uterine cavity in non-pregnant women is physiologically sterile, also as a premise to the long-held view that human infants develop in a sterile uterine environment, though likely reflecting under-appraisal of the extent of the human bacterial metacommunity. In an exploratory study, we aimed to investigate the putative presence of a uterine microbiome in a selected series of non-pregnant women through deep sequencing of the V1-2 hypervariable region of the 16S ribosomal RNA (rRNA) gene. Methods. Nineteen women with various reproductive conditions, including subfertility, scheduled for hysteroscopy and not showing uterine anomalies were recruited. Subjects were highly diverse with regard to demographic and medical history and included nulliparous and parous women. Endometrial tissue and mucus harvesting was performed by use of a transcervical device designed to obtain endometrial biopsy, while avoiding cervicovaginal contamination. Bacteria were targeted by use of a barcoded Illumina MiSeq paired-end sequencing method targeting the 16S rRNA gene V1-2 region, yielding an average of 41,194 reads per sample after quality filtering. Taxonomic annotation was pursued by comparison with sequences available through the Ribosomal Database Project and the NCBI database. Results. Out of 183 unique 16S rRNA gene amplicon sequences, 15 phylotypes were present in all samples. In some 90% of the women included, community architecture was fairly similar inasmuch B. xylanisolvens , B. thetaiotaomicron , B. fragilis and an undetermined Pelomonas taxon constituted over one third of the endometrial bacterial community. On the singular phylotype level, six women showed predominance of L. crispatus or L. iners in the presence of the Bacteroides core. Two endometrial communities were highly dissimilar, largely lacking the Bacteroides core, one dominated by L. crispatus and another consisting of a highly diverse community, including Prevotella spp., Atopobium vaginae , and Mobiluncus curtisii . Discussion. Our findings are, albeit not necessarily generalizable, consistent with the presence of a unique microbiota dominated by Bacteroides residing on the endometrium of the human non-pregnant uterus. The transcervical sampling approach may be influenced to an unknown extent by endocervical microbiota, which remain uncharacterised, and therefore warrants further validation. Nonetheless, consistent with our understanding of the human microbiome, the uterine microbiota are likely to have a previously unrecognized role in uterine physiology and human reproduction. Further study is therefore warranted to document community ecology and dynamics of the uterine microbiota, as well as the role of the uterine microbiome in health and disease.

ABSTRACT A recently introduced quantitative framework for gut microbiota analysis indicated that microbial load alterations can be linked to various diseases, making it essential to pinpoint its determinants. We identified nutrient load as a main driver of the quantitative microbial community composition and functionality in vitro by stepwise decreasing standardized feed concentrations from 100% to 33%, 20% and 10% in 5-day intervals. While the proportional composition and metabolic profile were mainly determined by the inter-individual variability (35% and 41%), nutrient load accounted for 58%, 23% and 65% of the observed variation in the microbial load, quantitative composition and net daily metabolite production, respectively. After the 10-fold nutrient reduction, the microbial load decreased by 79.72 ± 9% and 82.96 ± 1.66% in the proximal and distal colon, respectively, while the net total short-chain fatty acid production dropped by 79.42 ± 4.42% and 84.58 ± 2.42%, respectively. The majority of microbial taxa quantitatively decreased, whereas a select group of nutritional specialists, such as Akkermansia muciniphila and Bilophila wadsworthia, and a number of opportunistic pathogens remained unaffected. This shows that nutrient load is an important driver of the human gut microbiome and should be considered in future in vitro and in vivo dietary research. This study, performed in an advanced in vitro gastrointestinal model, identified nutrient load as an important driver of the gut microbial load, quantitative gut microbiome composition and metabolic functionality.

Oral diseases (e.g., dental caries, periodontitis) are developed when the healthy oral microbiome is imbalanced allowing the increase of pathobiont strains. Common practice to prevent or treat such diseases is the use of antiseptics, like chlorhexidine. However, the impact of these antiseptics on the composition and metabolic activity of the oral microbiome is poorly addressed. Using two types of oral biofilms—a 14-species community (more controllable) and human tongue microbiota (more representative)—the impact of short-term chlorhexidine exposure was explored in-depth. In both models, oral biofilms treated with chlorhexidine exhibited a pattern of inactivation (>3 log units) and fast regrowth to the initial bacterial concentrations. Moreover, the chlorhexidine treatment induced profound shifts in microbiota composition and metabolic activity. In some cases, disease associated traits were increased (such as higher abundance of pathobiont strains or shift in high lactate production). Our results highlight the need for alternative treatments that selectively target the disease-associated bacteria in the biofilm without targeting the commensal microorganisms.

Two by-products containing phenols and polysaccharides, a “pâté” (OP) from the extra virgin olive oil milling process and a decoction of pomegranate mesocarp (PM), were investigated for their effects on human microbiota using the SHIME® system. The ability of these products to modulate the microbial community was studied simulating a daily intake for nine days. Microbial functionality, investigated in terms of short chain fatty acids (SCFA) and NH4+, was stable during the treatment. A significant increase in Lactobacillaceae and Bifidobacteriaceae at nine days was induced by OP mainly in the proximal tract. Polyphenol metabolism indicated the formation of tyrosol from OP mainly in the distal tract, while urolithins C and A were produced from PM, identifying the human donor as a metabotype A. The results confirm the SHIME® system as a suitable in vitro tool to preliminarily investigate interactions between complex botanicals and human microbiota before undertaking more challenging human studies.

Abstract The rumen microbiome occupies a central role in animal health and productivity. A better understanding of the rumen ecosystem is essential to increase productivity or decrease methane production. Samples were collected from the three main rumen environments: the solid-adherent fraction, the liquid fraction and the epithelium. For the liquid and solid fraction, two alternative sample processing protocols were compared, resulting in a total of five sample types: crude solids (S), the eluted solid-adherent fraction (Ad), free-living species in the crude rumen liquid (CRL), strained liquid samples (Lq) and epimural scrapings (Ep). The bacterial and methanogen communities of these sample types were analysed using 16S metabarcoding and qPCR. The results indicate that the liquid and solid-adherent environments are distinguished mainly by the differential abundance of specific taxonomic groups. Cellulolytic bacteria that pioneer biofilm formation, together with secondary colonisers are prevalent in solid-adherent samples, while dominant species in the fluid samples are primarily identified as consumers of soluble nutrients. Also, methanogen species are found to have a preference for either a solid-adherent or free-living occurrence. The epimural environment is characterised by a different microbial profile. Ten bacterial families and two methanogen genera are almost exclusively found in this environment. The experiment and results described in this manuscript were aimed at increasing the understanding of the interactions between the complex microbial ecosystems of different rumen environments.

Postbiotics are a new category of biotics that have the potential to confer health benefits but, unlike probiotics, do not require living cells to induce health effects and thus are not subject to the food safety requirements that apply to live microorganisms. Postbiotics are defined as a “preparation of inanimate microorganisms and/or their components that confers a health benefit on the host”. Postbiotic components include short-chain fatty acids, exopolysaccharides, vitamins, teichoic acids, bacteriocins, enzymes and peptides in a non-purified inactivated cell preparation. While research into postbiotics is in its infancy, there is increasing evidence that postbiotics have the potential to modulate human health. Specifically, a number of postbiotics have been shown to improve gut health by strengthening the gut barrier, reducing inflammation and promoting antimicrobial activity against gut pathogens. Additionally, research is being conducted into the potential application of postbiotics to other areas of the body, including the skin, vagina and oral cavity. The purpose of this review is to set out the current research on postbiotics, demonstrate how postbiotics are currently used in commercial products and identify a number of knowledge gaps where further research is needed to identify the potential for future applications of postbiotics.

ObjectiveThe intestinal microbiota plays a central role in the development of many chronic inflammatory diseases including IBD and metabolic syndrome. Administration of substances that alter microbiota composition, including the synthetic dietary emulsifiers polysorbate 80 (P80) and carboxymethylcellulose (CMC), can promote such inflammatory disorders. However, that inflammation itself impacts microbiota composition has obfuscated defining the extent to which these compounds or other substances act directly upon the microbiota versus acting on host parameters that promote inflammation, which subsequently reshapes the microbiota.DesignWe examined the direct impact of CMC and P80 on the microbiota using the mucosal simulator of the human intestinal microbial ecosystem (M-SHIME) model that maintains a complex stable human microbiota in the absence of a live host.ResultsThis approach revealed that both P80 and CMC acted directly upon human microbiota to increase its proinflammatory potential, as revealed by increased levels of bioactive flagellin. The CMC-induced increase in flagellin was rapid (1 day) and driven by altered microbiota gene expression. In contrast, the P80-induced flagellin increase occurred more slowly and was closely associated with altered species composition. Transfer of both emulsifier-treated M-SHIME microbiotas to germ-free recipient mice recapitulated many of the host and microbial alterations observed in mice directly treated with emulsifiers.ConclusionsThese results demonstrate a novel paradigm of deconstructing host–microbiota interactions and indicate that the microbiota can be directly impacted by these commonly used food additives, in a manner that subsequently drives intestinal inflammation.