Scientific Substantiation of Population Monitoring of Free-Living ProtozoanCommunity in Natural Biotopes: Communication 2

Introduction: Studies of free-living protozoa cover a wide range of topics owing to their simplicity and variety of forms and functions in maintaining ecosystem balance in the microbiomes of reservoirs, soils, and human microbiota. Objective: To provide a scientific rationale for monitoring the circulation of free-living unicellular organisms of natural biocenoses in order to update and improve the Russian scientific and methodological research basis. Materials and methods: We conducted sanitary and hygienic, biological and parasitological studies of environmental samples, including 126 samples of wastewater and 360 samples of surface water, 30 samples of tap water, 210 samples of bottom sediments, 189 soil samples, and 300 samples of human feces taken in the Moscow Region in 2021–2023. Results: The protozoan index along the Moscow River ranged from null to 4.8 units/mL3 against the excessive total chloride level (Cl-); nucleic acids of viruses were determined in 11 types of ciliates; the contents of Cryptosporidium spp. and Lamblia spp. reached 4 lg and those of Blastocystis spp. and Entamoeba spp. were up to 6 lg. Contamination of tap water with cysts of Lamblia spp. was 3.2 %. The soil content of free-living protozoa in industrial areas was 2.1 times higher than in parks and 3.2 times higher than in residential areas (p = 0.0372). New data have been obtained on the effect of commensal amoebae Entamoeba spp. on changes in intestinal microbiota by the type of growth activation of five species of opportunistic bacteria. Conclusion: The paper outlines promising areas of sanitary (environmental) protistology within improvement of the scientific and methodological basis for the fundamental research into patterns of symbiotic relationships of free-living protozoa in the natural environment and in connection with medical aspects of applied research.