Anna Evgenievna Ivanova

Complexes of cultured saprotrophic bacteria and yeasts from different components of soil constructions (humus soil horizon and peat) were studied simultaneously with the assessment of auxin-producing activity (synthesis of 3-indolylacetic acid, IAA), of some bacteria and yeast strains isolated. The study was conducted at the stage of laying two variants of constructions in Syktyvkar, formed from components of local origin (variant 1) and imported (humus soil horizon, Moscow, peat "Seliger-agro", Tver region) (variant 2).

The taxonomic structure of microbial complexes isolated from the studied substrates had significant features of similarity. At the same time, components of variant 1 revealed a greater diversity of cultivated saprotrophic bacteria (Bacillus species) species resistant to adverse environmental conditions as well as the presence of psychrophilic basidiomycete yeast Leucosporidium scottii, which was not found in the components of variant 2.

The average IAA production by the yeast strains studied was 647.6 µg/L and by saprotrophic bacteria - 741.3 µg/L. The highest values of IAA concentration were found in the culture liquid of the yeast Tausonia pullulans (strain Y-6) - 3362.6 µg/l, isolated from the humus soil layer of variant 1, and of the two saprotrophic bacteria Flavobacterium рsychrophilum (strain B-7 - 2616.8 µg/L and B-5 - 1056.3 µg/L), isolated from the humus soil horizon in variant 1 and from peat of variant 2. For strains of the yeast Leucosporidium scottii and the cultured saprotrophic bacteria Flavobacterium psychrophilum the ability to synthesize IAA was found for the first time.