Andrey Antonovich Belov

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. 

Actinomycetes are key functional group of soil microorganisms that play a critical role in organic matter decomposition and the regulation of biogeochemical cycles in tropical ecosystems. This study provides a comprehensive analysis of actinomycete community structure and the physiological traits of cultivable strains in soils and litter from two protected areas in Southern Vietnam: Bidoup and Cat Tien Nature Reserves. We combined culture-based and molecular approaches, including quantification of cultivable actinomycetes, assessment of strain tolerance to abiotic stresses, evaluation of enzymatic activities, and high-throughput 16S rRNA gene sequencing to determine the taxonomic composition of prokaryotic communities. Actinobacteria were found to be dominant across soils, with clear differences between soils and litter. Litter communities were relatively uniform across elevations, whereas soil communities displayed pronounced variation. Cultured Streptomyces strains exhibited broad stress tolerance and high enzymatic activity, underscoring their ecological significance in tropical soil functioning.

Yu. V. Zakalyukina, A. R. Zaytsev, A. A. Belov, Yu. A. Zavgorodnyaya, M. V. Golichenkov The study assessed the impact of the nest-building activity of Camponotusvagus ants on the biological activity of microbial communities in the nest material compared to the surrounding soil. The objects of the study were samples from the aboveground and underground parts of theblack carpenter’s nest, built in a dead wood of Pinus sylvestris L., collected in the Ryazan region in a pine forest on humic arenosols. Using optical and scanning electron microscopy, a specific "nest material" was characterized, consisting of wood, plant debris and sand, densely woven with fungal mycelium, in which the presence of actinomycetes and unicellular bacteria forming associations was also shown. Comparative analysis of the elemental composition (C, N, P, S) demonstrated that this woody material is significantly enriched in all biophilic nutrients, and the C:N ratio in the nest material is effectively reduced compared to dead pine wood. The microbial community of the "nest material" was characterized by an increased intensity of processes involved in the nitrogen and carbon cycles (potential activity of nitrogen fixation, denitrification, CO₂ emission, and CH₄ production) compared to the microbial communities of the soil part of the nest and the control soil. Thus, during their nest-building activity in pine forests formed on poor sandy soils, Camponotusvagus ants intensify wood decomposition and thereby create unique habitats ("hotspots") with elevated biological activity. This underscores the important ecosystem function of carpenter ants. There are grounds to suggest possible symbiotic relationships between the ants and the mycelial microorganisms that form the so-called "nest material".

The article presents the results of an 18-month field experiment assessing the impact of 11 mulching substrates used in urban soils on a range of physical, chemical, and biological properties. The following substrates were studied: serpentine, marble, volcanic tuff, foam glass, coconut chips, painted and unpainted pine chips, large and small fractions of larch bark, and large and small fractions of pine bark. The substrates used were shown to have no negative impact on pH, total carbon (Corg) content, or its water-soluble forms (Cws), and no effect of the substrates on soil bulk density. The use of mulching substrates on urban soils contributed to an increase in the biological activity of the soil prokaryotic complex and a decrease in the number of sanitary-indicator and potentially pathogenic bacteria (Escherichia coli) in the soil, which reduces potential risks to the health of the urban population. The most favorable soil properties, based on the totality of the studied parameters, are formed under organic mulching substrates consisting of fine-sized particles, coconut chips and larch bark. An increase in the content of microscopic fungi in the upper horizon of urban soil under a 5-cm-thick mulch layer was detected. This may pose potential risks to human health due to the allergenic and potentially pathogenic properties of some soil micromycetes and requires further research. The obtained results allow us to recommend mulching urban soils with organic substrates not only for decorative purposes but also to enhance biological activity and, consequently, improve the biological condition of soils in anthropogenically transformed conditions.