Probiotics and Psychobiotics: the Role of Microbial Neurochemicals.

In light of recent data, microorganisms should be construed as organisms that are capable of communication and collective behaviors. Microbial communication signals are involved both in interactions among microbial cells within microbial social systems, including the human body-inhabiting microconsortium, and the dialog between the microbiota and the host organism. The microbiota inhabits various niches of the host organism, especially the gastrointestinal (GI) tract.

Adaptation and Probiotic Potential of Lactobacilli, Isolated from the Oral Cavity and Intestines of Healthy People.

The present study shows that, from 300 Lactobacillus strains isolated from the oral cavity and large intestine of 600 healthy people, only 9 had high antagonistic activity against pathogens and opportunistic pathogens. All antagonistic strains of lactobacilli have been identified by 16S rRNA sequencing and assigned to four species: Lactobacillus fermentum, Lactobacillus rhamnosus, Lactobacillus plantarum, and Lactobacillus casei. In addition, these lactobacilli appeared to be nonpathogenic and had some probiotic potential: the strains produced lactic acid and bacteriocins, showed high sensitivity to broad-spectrum antibiotics, and were capable of forming biofilms in vitro.

Role of Neurochemicals in the Interaction between the Microbiota and the Immune and the Nervous System of the Host Organism.

This work is concerned with the role of evolutionary conserved substances, neurotransmitters, and neurohormones, within the complex framework of the microbial consortium-immune system-nervous system axis in the human or animal organism. Although the operation of each of these systems per se is relatively well understood, their combined effects on the host organism still await further research. Drawing on recent research on host-produced and microbial low-molecular-weight neurochemicals such as biogenic amines, amino acids, and short-chain fatty acids (SCFAs), we suggest that these mediators form a part of a universal neurochemical "language.

Neuromodulatory effects and targets of the SCFAs and gasotransmitters produced by the human symbiotic microbiota.

The symbiotic gut microbiota plays an important role in the development and homeostasis of the host organism. Its physiological, biochemical, behavioral, and communicative effects are mediated by multiple low molecular weight compounds. Recent data on small molecules produced by gut microbiota in mammalian organisms demonstrate the paramount importance of these biologically active molecules in terms of biology and medicine.

[Role of Neuromediators in the Functioning of the Human Microbiota: "Business Talks" among Microorganisms and the Microbiota-Host Dialogue].

Current concepts concerning social behavior of the microorganisms inhabiting human gastrointestinal tract, as well as their role in the formation of integrated supracellular structures and in intercellular communication in the host-microbiota system are reviewed. Analysis of the literature data and the results obtained by the authors indicate an important role of neuromediators (biogenic amines, amino acids, peptides, and nitric oxide) in the intra- and interspecies microbial communication, as well as in the microbiota-host dialogue. The role of this dialogue for human health, its effect on human psyche and social behavior, and the possibility of construction of probiotic preparations with a goal-directed neurochemical effect are discussed.