The dissertation is devoted to the research of the microbial taxonomic diversity in extreme regions (Antarctica, the Dead Sea, the Crimea, lake Baikal, Ecuador) and their autecology, in particular resistance to extreme factors (UV radiation, dehydratation, hypersalinity, temperature). Phylogenetic analysis showed that terrestrial Antarctic ecosystems are inhabited by taxonomically diverse bacteria assigned to phylum Actinobacteria, Proteobacteria, Bacteroidetes, Firmicutes (genus: Frondihabitans, Microbacterium, Rhodococcus, Arthrobacter, Micrococcus, Rothia, Pseudomonas, Serratia, Sphingobacterium, Sporosarcina, Staphylococcus). Antarctic yeasts are presented by Basidiomycota (genus: Tremella, Rhodosporidium, Cryptococcus, Leucosporidiella, Leucosporidium, Rhodotorula) and Ascomycota (genus: Candida, Exophiala, Debaryomyces). About 80% of strains from natural Antarctic ecosystems are phsychrotolerant; up to 20% of strains are phsychrophilic, and up to 0,01% of strains are thermotolerant. We studied their resistance to extreme factors causing bacteriostatic or bactericidal effect on the majority of microorganisms. Representatives of the Actinobacteria and yeasts Exophiala, Rhodotorula are resistant to high doses of UV, namely up to 540 J/m2 and 1500 J/m2 respectively. The most of Proteobacteria strains are sensitive to UV. About 50% of the Antarctic microorganisms are halotolerant and resistant to dehydratation. Bacteria from the Antarctic and the Black Sea were shown to have correlation of their resistance to UV radiation and dehydration. The similar results were obtained for psychrotolerant Baikalian strains. About 80% of strains from the biofilm in the littoral zone (representatives of the Actinobacteria and Firmicutes) are resistant to UV (LD99,99 200 720 J/m2), while strains Serratia and Pseudomonas are highly sensitive to UV (LD99,99 35 70 J/m2). Strains isolated from the water and sediment (depth of 500 1400 m) lake Baikal are sensitive to UV. Chemoorganotrophic aerobic bacteria (up to 70%) from alpine ecosystems of Ecuador are halotolerant (growth in the range of 25 to 100 g NaCl/l), and resistant to UV radiation (LD99,99 800 1100 J/m2). Representatives of the phylum Firmicutes dominate in hypersaline ecosystems of the Crimea and the Dead Sea. All strains are thermotolerant (growth in the range of 20-50°С), halotolerant (growth in concentration of 100g NaCI/l medium), resistant to UV radiation (LD99,99 1100 1500 J/m2). Some strains of genus Bacillus have strong antagonistic effect on conditional-pathogenic test cultures Staphylococcus аureus and Candida аlbicans. The nucleotide sequences of 16S rRNA, 18S rRNA and 26S rRNA genes of the еxtremophilic and еxtremotolerant microorganisms were deposited in the GenBank sequence database and can be used further in phylogenetic analysis.
