Mucosal Immunity

Bacteroides spp. are members of the human gut microbiota that confer myriad benefits
on their hosts. Among them is the provision of energy from otherwise indigestible
polysaccharides comprising part of the host diet, lining the intestinal mucosal layer,
and decorating the surface of other microbes. Bacteroides spp. devote ∼20% of their
genomes to the transport and breakdown of a wide variety of polysaccharides, and to
the regulation of these processes. Bacteroides spp. rely on different families of
transcriptional regulators to ensure that carbohydrate utilization genes are expressed
under specific conditions.

Biofilms are slimy, microbial strongholds that grow in aqueous environments and typically adhere to surfaces. If you’ve ever taken a microbiology lab, you’

Article

The upper half of the human small intestine, known as the jejunum, is the primary site for absorption of nutrient-derived carbohydrates, amino acids, small peptides, and vitamins. In contrast to the colon, which contains 1011–1012 colony forming units of bacteria per ml (CFU/ml), the normal jejunum generally ranges from 103 to 105 CFU per ml. Because invasive procedures are required to access the jejunum, much less is known about its bacterial microbiota. Bacteria inhabiting the jejunal lumen have been investigated by classical culture techniques, but not by culture-independent metagenomics. The lumen of the upper jejunum was sampled during enteroscopy of 20 research subjects. Culture on aerobic and anaerobic media gave live bacterial counts ranging from 5.8 × 103 CFU/ml to 8.0 × 106 CFU/ml. DNA from the same samples was analyzed by 16S rRNA gene-specific quantitative PCR, yielding values from 1.5 × 105 to 3.1 × 107 bacterial genomes per ml. When calculated for each sample, estimated bacterial viability ranged from effectively 100% to a low of 0.3%. 16S rRNA metagenomic analysis of uncultured bacteria by Illumina MiSeq sequencing gave detailed microbial composition by phylum, genus and species. The genera Streptococcus, Prevotella, Veillonella and Fusobacterium, were especially abundant, as well as non-oral genera including Escherichia, Klebsiella, and Citrobacter. The jejunum was devoid of the genera Alistipes, Ruminococcus, Faecalibacterium, and other extreme anaerobes abundant in the colon. In patients with higher bacterial loads, there was no significant change in microbial species composition. The jejunal lumen contains a distinctive bacterial population consisting primarily of facultative anaerobes and oxygen-tolerant obligate anaerobes similar to those found in the oral cavity. However, the frequent abundance of Enterobacteriaceae represents a major difference from oral microbiota. Although a few genera are shared with the colon, we found no evidence for retrograde movement of the most abundant colonic microbes to the jejunum. Some individuals had much higher bacterial loads, but this was not correlated with decreases in bacterial species diversity or other evidence of dysbiosis.

When working stem cells within the intestine are depleted, some types of mature cells can transform themselves into stem cells, replenishing the population.

Food, antibiotics, and gender are just some of the factors that can throw off the balance between the gut and liver, according to the new study

Background We evaluated the effect of Saccharomyces boulardii CNCM I-745 on intestinal neuromuscular anomalies in an IBS-type mouse model of gastrointestinal motor dysfunctions elicited by Herpes Simplex Virus type 1 (HSV-1) exposure. Methods Mice were inoculated intranasally with HSV-1 (102 PFU) or vehicle at time 0 and 4 weeks later by the intragastric (IG) route (108 PFU). Six weeks after IG inoculum, mice were randomly allocated to receive oral gavage with either S. boulardii (107 CFU/day) or vehicle. After 4 weeks the following were determined: a) intestinal motility using fluorescein-isothiocyanate dextran distribution in the gut, fecal pellet expulsion, stool water content, and distal colonic transit of glass beads; b) integrity of the enteric nervous system (ENS) by immunohistochemistry on ileal whole-mount preparations and western blot of protein lysates from ileal longitudinal muscle and myenteric plexus; c) isometric muscle tension with electric field and pharmacological (carbachol) stimulation of ileal segments; and d) intestinal inflammation by levels of tumor necrosis factor α, interleukin(IL)-1β, IL-10 and IL-4. Results S. boulardii CNCM I-745 improved HSV-1 induced intestinal dysmotility and alteration of intestinal transit observed ten weeks after IG inoculum of the virus. Also, the probiotic yeast ameliorated the structural alterations of the ENS induced by HSV-1 (i.e., reduced peripherin immunoreactivity and expression, increased glial S100β protein immunoreactivity and neuronal nitric oxide synthase level, reduced substance P-positive fibers). Moreover, S. boulardii CNCM I-745 diminished the production of HSV-1 associated pro-inflammatory cytokines in the myenteric plexus and increased levels of anti-inflammatory interleukins. Conclusions S. boulardii CNCM I-745 ameliorated gastrointestinal neuromuscular anomalies in a mouse model of gut dysfunctions typically observed with irritable bowel syndrome.

Production of active TGF-β is regulated at a posttranslational level and implies release of the mature cytokine dimer from the inactive, latent TGF-β precursor. There are several cell-type specific mechanisms of TGF-β activation. We identified a new mechanism operating on the surface of human regulatory T cells and involving membrane protein GARP, which binds latent TGF-β1. The paracrine activity of regulatory T cell–derived TGF-β1 contributes to immunosuppression and can be inhibited with anti-GARP Abs. Whether other immune cell types use surface GARP to activate latent TGF-β1 was not known. We show in this study that stimulated, human B lymphocytes produce active TGF-β1 from surface GARP/latent TGF-β1 complexes with isotype switching to IgA production.

#12,621 One of the great inequities of life is that some people are at a higher risk of experiencing severe flu infection

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