Relevance. Professional activity of operational staff of the Russian EMERCOM in the Arctic zone is associated with adaptive changes in the body resulting in changes in all types of metabolism, appearance of functional abnormalities and, without proper correction, development of various diseases. The complex system of metabolic interaction between humans and the microbiota is well described by the “microbiota-gut-brain” axis, which includes endocrine, immune, and neurohumoral pathways. Dysfunction of this axis in humans may be involved in pathogenesis of various diseases and somatic psychoneurological disorders.Intention is to study features of the intestinal microbiota in operational staff of the Russian EMERCOM working in the adverse conditions of the Arctic zone.Methodology. A study group included 94 firefighters and rescuers of the Russian EMERCOM working in the Arctic zone of Russia and was divided into subgroups depending on relevant work experience (0–5 years, 6–10 years, 11 years and more), as well as on age (22–35 years and 36–56 years). A control group included 98 rescue workers from the North-West regional search and rescue team and employees of the territorial fire departments of St. Petersburg (males aged 32.1 ± 0.5 years). Quantity and composition of the parietal intestinal microbiota were assessed based on microbial markers in the blood plasma using gas chromatography-mass spectrometry.Results and Discussion. Negative changes in the quantity and structure of the parietal intestinal microbiota were revealed in operational staff of the Russian EMERCOM working in the Arctic zone of Russia as compared with the control group: the total number of microbial markers was reduced by 34 %, beneficial flora – by 44 %, opportunistic flora – by 10 %, aerobes – by 25 %, anaerobes – by 32 %. In the structure of beneficial microflora, the proportion of Lactobacillus was 1.5 times greater and the proportion of Bifidobacterium was 3 times fewer. The most pronounced changes in the intestinal microbiota with increase of work experience were found in rescuer workers (a decrease in opportunistic flora and aerobes, an increase in the ratio of anaerobic to aerobic flora). According to the Kruskal–Wallace test, the amount of microbial markers of Bifidobacterium, Propionibacterium/Cl. Subterminale, aerobes, endotoxin, as well as the ratio of anaerobic to aerobic flora depends on the work experience of operational staff of the Russian EMERCOM working in the Arctic zone of Russia.Conclusion. Ecological and professional stress in operational staff of the Russian EMERCOM working in the Arctic zone disturbs trophism of various types of endogenous microflora and its regulatory relationships with the human body and, hence, results in quantitative and qualitative changes in the composition of the microflora.