ИСТИНА

Many Antarctic microfungal strains, owing to the longtime geographical isolation and extremely severe climate of the continent, have developed peculiar genetic and physiological features. In particular, they are capable of producing secondary metabolites which account for their survival in extremely cold and dry conditions. Among these metabolites new cold-active antibiotics and enzyme may be found. The aim of this work was the screening for the antimicrobial activity of 31 microfungal strains isolated from Antarctic soils ("stone pavements", "ahumic soils", endoliths, soils from moss and lichen cover, gleezems). The objects for the research were strains of Antarctomyces psychrotrophicus, Ascochyta pisi, Aspegillus fumigatus, Aspergillus sclerotiorum, Atradidymella muscivora, Botrytis cinerea, Hyphozyma variabilis, Cladophialophora minutissima, Cladosporium tenuissimum, Clonostachys rosea, Cylindrocarpon obtusisporum, Epicoccum nigrum, Eurotium niveoglaucum, Exophiala tremulae, Lecanicillium fungicola, Leptosphaeria coniothyrium, Leuconeurospora polypaeciloides, Microsphaeropsis olivacea, Microascus cinereus, Talaromyces flavus, Paecilomyces marquandii, Penicillium roseo-purpureum, P. simplicissimum, Periconia igniaria, Phialocephala lagerbergii, Phoma leveillei, P. violacea, Sarocladium kiliense, Thelebolus microsporus, T. ellipsoideus, T. globosus. The strains were cultivated on Czapek's agar and glucose-peptone-yeast agar (GPY). The antimicrobial activity was tested against test cultures of Bacillus subtilis ATCC 6633, Aspergillus niger INA 00760, Candida albicans ATCC 2091, as well as Antarctic bacterial strains: Gram-negative (Bosea sp., Brevundimonas sp., Delftia acidovorans, Pseudomonas sp., Ralstonia sp., Sphingomonas sp., Sphingopyxis sp., Stenotrophomonas sp., Variovorax sp.), Gram-positive (Arthrobacter sp., Bacillus megaterium) and actinomycetes (Streptomyces tanashiensis, S. venezuelae) at +25ᴼC using the agar block and the agar well diffusion methods. Antibiotic activity of all strains, except Hyphozyma variabilis, was shown to be higher on the rich GPY medium, than on Czapek's medium. Most eurytopic microfungi exhibited only antifungal activity, while psychrotolerant strains (Antarctomyces psychrotrophicus, Cladophialophora minutissima, Hyphozyma variabilis, Exophiala tremulae, Phoma leveillei, P. violacea, Thelebolus microsporus, T. ellipsoideus, T. globosus) showed exclusively antibacterial activity. The highest activity (inhibitory zone of 20-25 mm) against Bacillus subtilis was exhibited by strains of Antarctomyces psychrotrophicus and Hyphozyma variabilis. All of the studied strains suppressed (inhibitory zone of 2-15 mm using the agar block method) growth only of Gram-positive bacteria and actinomycetes. Cultural broths of some microfungi (A. sclerotiorum, E. niveoglaucum, L. fungicola, T. flavus) slightly (1-2 mm) suppressed growth of several strains of Antarctic Gram-negative bacteria. None of the tested psychrotolerant microfungi inhibited growth Aspergillus niger. The antagonistic activity of the Antarctic microfungal strains was well-evident against a wide range of native Gram-positive bacteria, being less evident against the test culture of Bacillus subtilis.The work was supported by the Russian Science Foundation grant №14-50-00029.