Regarding qualitative methods for evaluating human microbiota in an artificial environment

Objective. To study the dynamics of human intestinal microbiota under conditions of artificial isolation (simulating space flights) using a new eubiotic index that evaluates the balance of opportunistic and opportunistic microorganisms. Materials and methods. Data: archival materials of the Soviet space programs (1960-1980) and modern isolation experiments (“Sphinx”: 60 days; “Sirius”: 120/240 days; “Mars-500”: 520 days). Methodology: classical seeding on nutrient media to count microorganism colonies. Index I: calculated based on the priority of bacterial colonization. Statistical processing: Shapiro-Wilk, Kruskal-Wallis, ANOVA, Dunn test (StatTech v3.0.9 and R programs). Results. Short-term isolation (up to 15 days): Peak of the eubiotic index on days 8-11 with subsequent decrease (approximation: R² = 0.9986). Long-term isolation (60-520 days): Steady decrease in the eubiotic index I, reaching a minimum on days 150-300 (I < 1 - dominance of opportunistic microflora). Probiotics slow down, but do not prevent dysbiosis. Model verification: good agreement with the Sphinx experiment. Conclusion. Isolation causes a decrease in the diversity of microbiota and a shift in the balance towards opportunistic microorganisms. The following are recommended for long-term space missions: integration of prebiotics into the diet; personalized probiotics.