DETECTION OF VIABLE YEAST IN 3-MILLION-YEAR-OLD PERMAFROST SOILS OF SIBERIA

It was established that viable yeast occur in significant amounts (up to 9000 colony-forming units per gram of absolutely dry soil) in certa in layers of permafrost soils of Siberia with an estimated age of abou t 3 million years. Thus, despite the complexity of the organization of the eukaryotic cell, eukaryotic microorganisms proved as resistant un der the conditions of Siberian permafrost soils as prokaryotes. The st rains isolated were classified into three genera of basidiomycetes: Cr yptococcus, Rhodotorula, and Sporobolomyces. The properties of two str ains allowed us to identify them as Cryptococcus albidus (Saito) Skinn er and Sporobolomyces roseus Kluyver ct van Niel. The yeast strains cl assified into the genus Rhodotorula resembled representatives of the s pecies Rh. muscorum and Rh. mucilaginosa, but differed from them in a number of diagnostic characteristics.