Molecular Language of Symbiotic Gut Microorganisms

Abstract

In the 1990s, it was found that various microorganisms, their cell fragments, colloid particles, food starch granules and other compounds similar in size to bacterial cells or smaller can easily penetrate intestinal mucosa. Owing to contemporary chromatography and mass spectrometry methods, many similar low molecular weight particles and molecules are easily detectable in blood, urine and other human biological fluids. Their appearance in these fluids can be detected as early as a few minutes after oral administration of any given indicator compounds or microorganisms (Freter and Nader de Macias 1995; Osipov and Verkhovtseva 2011). It was shown clinically and experimentally that effects of probiotics on human and animal organisms arise in case of administration not only of live but also of killed (by heating, radiation etc.) microorganisms, as well as their cell-free extracts, purified cell walls, supernatants of culture fluids for bifidobacteria and lactobacilli (Lee et al. 2002; Reading and Sperandio 2006). The results of such studies have convincingly demonstrated that the translocation of probiotic bacteria, their cell fragments, metabolites and signaling molecules, as well as low molecular weight compounds formed as a result of microbial degradation of epithelial cells, saliva, intestinal juices, food substrates from the intestinal lumen is a common physiological process. Biologically active compounds (autoinducers) associated with the metabolic activity of symbiotic (probiotic) microorganisms can potentially modify and take part practically in any physiological function, metabolic, signaling, behavioral reaction, in intra- and intercellular information exchange. Given that, the mechanisms of their effects may be different in different symbiotic and probiotic microorganisms. Autoinducers (chemokines, modulins) of microbial nature allow symbiotic microorganisms to discern the environment, interact with each other and with host cells. These molecules trigger a cascade of processes in prokaryotic and eukaryotic cells, when their quantity reaches a certain level (“quorum”). Autoinducers interact with cell receptors, with regulatory proteins recognizing them and, in the long run, activate (induce) the work (expression) of the corresponding genes in the DNA of microbial, mitochondrial and eukaryotic host cells. Thanks to autoinducers, microorganisms and cells of macroorganism exchange the information and coordinate their activity. That is why such signaling molecules are viewed in scientific literature as “words” in the molecular information “language”.