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Fungi able to survive under the extreme environment of soda lakes remain poorly studied. This paper presents data on the diversity and ecophysiology of filamentous fungi inhabiting one of the most alkaline habitats of the Earth: Lake Magadi, where pH values may exceed 11-12. The lake is home to a large number of prokaryotes, which form complex communities with algae and some other eukaryotes. In this study, 22 species of filamentous fungi isolated from soil samples collected on the coastline of Lake Magadi have been characterized using a systematic approach, which includes selective isolation, an analysis of morphological traits, molecular-genetic analysis, growth experiments to determine pH and temperature preferences, and an analysis of the dependence on NaCl concentrations. According to the results, alkaline soil from the Lake Magadi coastline is colonized by fungi with differing types of adaptation to high pH values. Alkaliphilic and alkalitolerant fungi belong to different families of Ascomycetes, mainly to Plectosphaerellaceae, as well as to Onygenaceae, Trihocomaceae, and Pleosporaceae. Sodiomyces tronii and S. magadii are new obligate alkaliphilic species within the earlier monotypic genus Sodiomyces (Plectosphaerellaceae). According to the growth experiments, obligate alkaliphilic isolates demonstrate thermo- and halotolerant properties. The problems of adaptation to the external pH, possible substrate preferences, and association of alkaliphilic fungi with other organisms are discussed. [ABSTRACT FROM AUTHOR]