Microorganisms associated with epithelial surfaces and stability of the indigenous gastrointestinal microflora

Abstract

Indigenous microorganisms of many genera and species associate with mucosal epithelia in the gastrointestinal tracts of animals and humans. These mechanisms may involve a high degree of specificity for host and surface habitat. They may include a capacity of the microorganisms to adhere to the membranes of substratum epithelial cells, to colonize and utilize as a source of nutrients the mucus overlying epithelial cells, and to be motile and attracted into the mucous layer by chemotaxis. The microbes must be able as well to thrive in the nutritional and environmental conditions prevailing on the epithelial surfaces. Microbial communities associated with epithelial surfaces are critical for maintaining a microflora in areas of the tract (i.e., stomach, small intestine) where the lumenal content moves at a rate exceeding the maximum rates at which indigenous microorganisms can multiply. Such communities even may be important in areas (i.e., the cecum and colon) where the content moves at rates below those at which the microbes can multiply. In such areas, microorganisms colonizing mucus on the epithelium and in the crypts of Lieberkuhn may provide a stable inoculum for the lumenal content which may be altered in composition in times of dietary change. Microorganisms associated with gastric and intestinal surfaces undoubtedly serve in a major way to stabilize the composition of the indigenous gastrointestinal microflora. At the molecular level, however, little is known about the mechanisms stabilizing the composition or the biochemical and genetic activities of the microflora. Such mechanisms are important subjects for research in the future.

Effect of organic acids on inhibition of Escherichia coli O157:H7 colonization in gnotobiotic mice associated with infant intestinal microbiota

“…From the viewpoint of this in vivo report, flagellar motility represents an important advantage for newly introduced bacteria in moving towards favourable conditions or in avoiding detrimental environments, and it may allow flagellated bacteria to successfully compete with other microorganisms (Fenchel 2002). In addition to the locomotive properties, motility is an important factor for bacterial colonization in the mucus layer of the intestine (Savage 1987), and also motility in pathogenic microorganisms is usually considered to be essential for colonization of the host organism (Josenhans and Suerbaum 2002;Ottemann and Miller 1997;Postnova et al 1996). Therefore, bacterial motility could be related to bacterial persistence in the intestinal tract, and the different caecal population count of E. coli O157:H7 between GB-3 and GB-4 might result from different motility due to the different profiles of organic acids.…”

Intestinal Shiga Toxin-Producing Escherichia coli Bacteria Mitigate Bovine Leukemia Virus Infection in Experimentally Infected Sheep

“…Intestinal flora is a complex system of microbial communities characterized by host and spatial specificity with remarkable stability and is refractory to change by external interventions (21,44). Therefore, it may not be surprising that oral treatments with STEC, although substantial, had a limited impact on the fecal STEC numbers in sheep and, in some cases, even failed to bring a change in host status from fecal STEC negative to fecal STEC positive.…”

Bacteria, phages and pigs: the effects of in-feed antibiotics on the microbiome at different gut locations

“…In fact, the distal small intestine (ileum) harbored a greater richness of bacteria on the mucosa compared with the lumen. (Savage, 1987) proposed that the mucosal bacterial populations in the gut both stabilize the intestinal community and prevent pathogens by providing a constant, established inoculum for the lumen to complete the breakdown of non-digested food substrates (Williams et al, 2011). Perhaps the mucosal bacteria of the ileum serve as an inoculum for the large intestine.…”