“Commensal bacterial communities residing within the intestinal lumen of mammals have evolved to flourish in this microenvironment. To preserve this niche, commensal bacteria act with the host to prevent colonization by invasive pathogens that induce inflammation and disrupt the intestinal niche commensal bacteria occupy. Thus, it is mutually beneficial to the host and commensal bacteria to inhibit a pathogen’s ability to establish an infection. Commensal bacteria express factors that support colonization, maximize nutrient uptake, and produce metabolites that confer a survival advantage over pathogens. Further, commensal bacteria stimulate the host’s immune defenses and drive tonic expression of anti-microbial factors. In combination, these mechanisms preserve the niche for commensal bacteria and assist the host in preventing infection.” Commensal bacteria mediated defenses against pathogens
“Research over the past decade has demonstrated a surprising role for the gut microbiome in normal brain development and function. In this review we postulate that perturbations in the gut microbial-derived nutrient supply, driven by environmental variation, profoundly impacts upon normal brain development and function.”
“Increasing evidence suggests that perturbations in the intestinal microbiota composition of infants are implicated in the pathogenesis of food allergy (FA), while the actual structure and composition of the intestinal microbiota in human beings with FA remain unclear. “
“The way in which our gut bacteria interact with each other may have vital implications for the risk of developing type 1 diabetes, according to new research.”
“Pooperoni? Spanish researchers produce low sodium and fat probiotic stool sausage. A fermented sausage product that is made with probiotic lactobacilli bacteria isolated from infant faeces could transform the meat product in to a health food, according to new research.” 
“Bacteriocins, which are antimicrobial peptides produced by certain bacteria, might warrant serious consideration as alternatives to traditional antibiotics. These molecules exhibit significant potency against other bacteria (including antibiotic-resistant strains), are stable and can have narrow or broad activity spectra. Bacteriocins can even be produced in situ in the gut by probiotic bacteria to combat intestinal infections. Although the application of specific bacteriocins might be curtailed by the development of resistance, an understanding of the mechanisms by which such resistance could emerge will enable researchers to develop strategies to minimize this potential problem” 
“”Contrary to this view, recent findings suggest that IBS is linked to clearly detectable gut microbiota alterations. Additionally, bloating can be related to specific kinds of diet, thus opening up promising paths towards an efficient disease management,” says Professor Giovanni Barbara (University of Bologna, Italy). ..there is a lot of evidence showing that IBS is associated with an imbalanced composition of the gut microbiota. This means that the system of checks and balances between beneficial and potentially harmful bacteria, which characterizes a healthy gut microbiota, is disturbed in IBS patients… those IBS patients who have several clear-cut gut symptoms have also more profound changes in their gut microbiota, as compared to other patients whose bowel physiology is less disturbed, but instead combined with mood disorders. “
“Bacteria alter the gut permeability by tight junction disassembling and/or actin contraction” i.e. Leaky Gut may be caused by bacteria.
” Industry must do more to understand the inter-species interactions of multi-strain probiotic products rather than assuming that ‘more is better’, warns Professor Gregor Reid.” 
“We all rely on trillions of bacteria in our gut to break down certain components of our diet. One example is phytate, the form phosphorus takes in cereals and vegetables. Broken down phytate is a source of vital nutrients, but in its undigested form it has detrimental properties. It binds to important minerals preventing them being taken up by the body, causing conditions like anemia, especially in developing countries. Phytate also leads to excess phosphorus leaching into the soil from farm animal waste, and feed supplements are used to minimize this.” 
“Modifications to the microbiota could lead to changes in health and lifespan that are associated with aging” 
” Here we show that the short-term consumption of diets composed entirely of animal or plant products alters microbial community structure and overwhelms inter-individual differences in microbial gene expression. The animal-based diet increased the abundance of bile-tolerant microorganisms (Alistipes, Bilophila and Bacteroides) and decreased the levels of Firmicutes that metabolize dietary plant polysaccharides (Roseburia, Eubacterium rectale and Ruminococcus bromii). Microbial activity mirrored differences between herbivorous and carnivorous mammals, reflecting trade-offs between carbohydrate and protein fermentation” 
“Streptococcus salivarius is one of the first colonizers of the human oral cavity and gut after birth and therefore may contribute to the establishment of immune homeostasis and regulation of host inflammatory responses. The anti-inflammatory potential of S. salivarius was first evaluated in vitro on human intestinal epithelial cells and human peripheral blood mononuclear cells. We show that live S. salivarius strains inhibited in vitro the activation of the NF-κB pathway on intestinal epithelial cells. We also demonstrate that the live S. salivarius JIM8772 strain significantly inhibited inflammation in severe and moderate colitis mouse models. ”  – this is available as an oral probiotics.
” Using a mouse model, US researchers have linked neurodevelopmental symptoms similar to those seen in autism spectrum disorder (ASD) patients to changes seen in the bacteria in the animals’ guts.ASD is diagnosed when individuals exhibit characteristic behaviours that include repetitive actions, decreased social interactions, and impaired communication. Many individuals with ASD also suffer from gastrointestinal (GI) issues, such as abdominal cramps and constipation”
“It’s a landmark study,” Rob Knight, a microbial ecologist at the University of Colorado, Boulder, who was not involved with the work, told ScienceNOW. “It changes our view of how rapidly the microbiome can change.”
In 2009, Turnbaugh’s team had shown a similar effect in mice: a change in diet could affect the murine gut microbiome in a single day, in fact. To see if the results would hold up in people, Turnbaugh, along with Lawrence David from Duke University and their colleagues, fed five volunteers a high-protein diet, with meals of bacon and eggs for breakfast, spareribs and brisket for lunch, and salami and cheese for dinner. This group could also snack on pork rinds and string cheese. The high-fiber group, on the other hand, got fruits, vegetables, grains, and beans. Before, during, and after the diet change, the team collected stool samples from each participant to assess the bacterial composition of their guts, as well as the gene expression activity of those microbes.
Before the week was up, the researchers found noticeable differences in the gut bacteria of the two treatment groups. The meat-eaters harbored more bacteria that are able to tolerate high levels of bile acids, which are secreted by the body to help digest meat. The bacteria isolated from this group also appeared to increase expression of genes involved in breaking down proteins. Plant-eaters, on the other hand, had fewer bile-resisting bacteria and higher expression levels of gene associated with carbohydrate digestion”
” In humans, having a severe viral infection raises the risk that a
pregnant woman will give birth to a child with autism. Patterson and his lab
reproduced the effect in mice using a viral mimic that triggers an
infection-like immune response in the mother and produces the core
behavioral symptoms associated with autism in the offspring…. the researchers treated the mice with Bacteroides fragilis, a bacterium that has been used as an experimental probiotic therapy in animal models of GI disorders. The result? The leaky gut was corrected.
In addition, observations of the treated mice showed that their behavior had
changed. In particular, they were more likely to communicate with other
mice, had reduced anxiety, and were less likely to engage in a repetitive
digging behavior. “The B. fragilis treatment alleviates GI problems in the mouse model and also improves some of the main behavioral symptoms,” Hsiao says. “This suggests that GI problems could contribute to particular symptoms in
neurodevelopmental disorders.””