— A comprehensive study of prokaryotic communities of zonal Ferralsols and intrazonal Fluvisols, as well as associated leaf litter and “suspended” soil from epiphytic fern baskets was carried out. The maximum number of bacteria determined by the direct luminescence method (5.59 billion cells) was found in the samples of Fluvisols, while the lengths of fungal (2038 m/g) and actinomycete (1086 m/g) mycelia were the largest in the mountainous Ferralsols. Bacteria of the genus Streptomyces included in the saprotrophic bacterial complex of the studied substrates made a significant contribution to the destruction of plant material. The bacteria of the phyla Firmicutes (80%) and Proteobacteria (15%) predominated in the prokaryotic community of the zonal Ferralsols, while the phyla Proteobacteria (51%) and Actinobacteria (38%) dominated in the sample of the “suspended” soil. The phyla Chloroflexi, Acidobacteria, Bacteroidetes, and Cyanobacteria were significantly less represented. Against the background of significant differences between the studied prokaryotic communities at the level of genera, they were characterized by similar functional groups of microorganisms: xenobiotic decomposers, nitrogen cycle bacteria, extremophiles, as well as bacteria that inhibit the growth of micromycetes. The metabolically active part of the prokaryotic community represented by the phyla Proteobacteria, Actinobacteria, and Acidobacteria, was the highest in the “suspended” soil and the least active in the leaf litter and A horizon of Ferralsols, which correlated with the high abundance of these phyla and the significant taxonomic diversity of bacteria in this locus. Functional genes nifH and alkB encoding nitrogenase and alkane-hydroxylase, respectively, were detected in all studied substrates. The number of copies of functional genes was the highest in the “suspended” soil sample, which makes this locus promising for isolating strains with a high biotechnological potential.

Epifluorescence microscopy revealed the presence of bacteriophages in all samples of the studied soils (Haplic Chernozem, Albic Retisol (Cutanic, Siltic), Haplic Kastanozem, Fluvisol (Loamic, Humic)), Limnic Fluvisol, Dystric Fibric Histosol, Histic Leptosol, and Arenosol). The number of bacteriophages counted using the SYBR Green I dye was significant: 0.34–5.7 billion units/g soil. Transmission electron microscopy was used to determine the icosahedral, caudate, and filamentous morphotypes of bacteriophages. Comparison of the amount of bacteriophages and bacteria showed that the number of phages in the studied soil samples was slightly lower as compared to bacteria (except for the samples from Chernozem and from the Antarctic Arenosol, where the number of phages slightly exceeded that of bacteria). The ratio between the numbers of bacteriophages and bacteria varied from 0.16 to 1.67. The number of cells of gram-negative and gram-positive bacteria was determined using the L7005 dye and compared with the number of bacteriophages in samples of Histosol and Kastanozem. The predomination of gram-negative bacteria (61% of the total number of bacteria) was recorded. The number of phages in the waterlogged biotope (Histosol) was three times higher than in the dry biotope (Kastanozem). The revealed high abundance and significant morphological diversity of phages enable us to suggest their particular role in the regulation of the number of bacteria in soils.

The quantitative and qualitative characteristics are given of the soil prokaryotic communities in the Dystric Fluvisol, litter, and "suspended soil" in epiphyte baskets. The number of bacteria (direct luminescence method) varied from 1.1 to 2.6 billion cells/g soil and was the highest in the suspended soil sample and lower in the litter and A and AB horizons of Dystric Fluvisol (brown meadow alluvial soil). Proteobacteria, Actinobacteria, and Acidobacteria predominated in the prokaryotic community (at the phylum level); Chloroflexi, Firmicutes, and Verrucomicrobia were found in smaller amounts; the content of Nitrospirae, Planctomycetes, and Gemmatimonadetes was even lower. Representatives of the Archaea domain were found in the A horizon and in the suspended soil. Their content was significantly lower than that of the Bacteria domain and did not exceed 1%. Archaea were represented by the Thaumarchaeota and Euryarchaeota phyla in the A horizon and by Thaumarchaeota and Woesearchaeota phyla in the suspended soil. Based on the calculated ecological indices (alpha and beta diversity, measures of similarity by Bray-Curtis metrics and weighted UniFrac), it was shown that the microbiome of the suspended soil was closer to the microbiome of A horizon of Dystric Fluvisol than to the microbiome of litter. The metabolically active part of the prokaryotic community represented by the Proteobacteria, Actinobacteria, and Acidobacteria phyla reached its maximum in the suspended soil and was lower in the litter and A horizon of Dystric Fluvisol, and this correlated with the high abundance of these phyla and the significant taxonomic diversity of bacteria in this locus. Functional genes (nifH and alkB) were detected in all studied substrates. The number of copies of functional genes was the highest in the suspended soil sample, which makes this locus promising for isolating the strains with high biotechnological potential.

Abundance and diversity of cultivated bacteria in saprotrophic soil complexes were monitored for two years on the territory of one of the large industrial cities of the European North of Russia, Syktyvkar. The analysis was carried out before and after quarantine due to the COVID-19 pandemic. The city of Syktyvkar is characterized by a high population and intensive anthropogenic pressure. According to the total indicators of the current state of the environmental components, it should belong to the tense category, by environmental standards. Studies were conducted in 2019–2020. Topsoils (0–10 cm) of urbanozems and horizon A in the park area in the urban space, as well as zonal undisturbed podzolic soil, were analyzed. Comparison of the two-year monitoring results demonstrated a marked increase in the number and diversity of saprotrophic bacterial complexes in 2020 in both urban and control soils (topsoil, 0–10 cm). Due to a sharp and prolonged decrease in the anthropogenic impact on the environment during quarantine measures, content of the bacteria of the families Enterobacteriaceae including sanitary-indicative ( Escherichia coli , Enterococcus faecalis ) and opportunistic and allergenic ( Enterobacter agglomerans , Citrobacter europaeus , Klebsiella oxytoca , Serratia marcescens , etc.) in the urbanozems decreased. This can be considered as a manifestation of the soil’s ability to “self-remediate” during a decrease in anthropogenic impact on the environment.

The main components of solid atmospheric aerosol are soil and rock particles raised from the earth’s surface by wind erosion, and primary biological aerosol particles. In the composition of atmospheric aerosol, many pollutants, both mineral and organic, appear in areas with intensive human activity. Summer dust (solid atmospheric fallouts) that fell out of atmosphere was collected at two sites in Moscow (the territory of the Leo Tolstoy Museum-Estate in Khamovniki and the Botanical Garden of the Biological Faculty of Moscow State University). Morphological and microbiological studies were carried out in order to characterize the composition of the organic part of urban solid atmospheric fallouts and its possible impact on soils and the urban ecosystem as a whole. It has been found that the composition of the organic part of the samples was identical and included: the representatives of aeroplankton and other particles of biological origin, and also fragments of oil films, plastic fibers, carbon particles, etc., which indicated the hydrocarbon and microplastic pollution brought from the atmosphere. The composition of the studied groups of microorganisms in atmospheric fallouts and in urban soils was similar and indicated close ecological links between urban dust aerosol and soils. The biomass of the studied groups of microorganisms of atmospheric solids was dominated by fungi, many of which are potentially pathogenic and allergenic organisms. Apparently, atmospheric solid aerosols are carriers of microbiological pollution associated with animal feces in the city. The presence of such particles in the air indicates insufficient soil activity as a “bacterial filter”.

In Albic Retisols, Stagnic Fluvisols and Gleyic Fluvisols processes of ferriferous and manganese transformation follows rather active, that create new ecological niches for soil microorganisms.The study of concretions in the Albic Retisols, Stagnic Fluvisols and Gleyic Fluvisols showed, that the most characteristic feature of the prokaryotic community was the higher number and diversity of recoverable bacteria in comparison with the same indexes in the host horizons. The representatives of phylum Proteobacteria (class Gammaproteobacteria and Deltaproteobacteria) were dominant in the microbial communities in studied concretions. For the first time, the bacteriophages were found in concretions among them tailed phages were dominant. The method of the high-throughput sequencing of the 16S rRNA gene allowed to reveal the variability of the prokaryotic community in concretions of the Albic Retisol (Cutanic, Siltic), which was characterized predominantly by 7 bacterial phyla and 2 archaea phyla Both groups of organisms typical of soils and prokaryotes capable of transformation of iron and manganese under aerobic and anaerobic conditions were revealed in soil concretions. The specific characteristic of the studied soil concretions was a widespread occurrence of filtered bacterial forms, which may be considered as specific survival forms in soil loci.

Urbanozems (Urbic Technosols) contaminated by heavy metals and polychlorbiphenyls (Urbic Technosols Toxic) and intruzems (Urbic Technosols Toxic) were studied in Moscow; additionally, we studied recreazems (Urbic Technosols Thaptohumic) and culturozems (Urbic Technosols Pantohumic) on the territory of the Botanical Garden of Moscow State University (Aptekarskii Ogorod, the Apothecaries’ Garden). In the soils contaminated with heavy metals and oil products, the number of viable cells of bacteria decreased, whereas the content of filterable forms of bacteria increased. The taxonomic structure of saprotrophic bacterial complexes in contaminated urban soils was transformed towards an increase in the diversity of bacterial taxa atypical of natural undisturbed soils. Rhodococci ( Rhodococcus genus) predominated in the soils contaminated with oil and polychlorbiphenyls, enterobacteria ( Escherichia, Enterobacter , and Klebsiella genera) predominated in the soils contaminated with municipal wastes, and Arthrobacter genus was dominant in the soils contaminated with cement dust. Soils of both Botanical Gardens of Moscow State University were characterized by the high population density and specific distribution of bacteria in the profile; the structure of their saprotrophic bacterial complex had some similarity with that in the soils of more southern regions. The obtained data on the bacterial diversity of urban soils attest to considerable transformation of bacterial communities both in the contaminated urban soils and in the soils of botanical gardens.

Comparative study of microbial communities in red ferralitic soil, as well as tree waste and phylloplane of woody plants, of Varadero National Park (Cuba) has been performed. It is shown that the total bacterial abundance and the length of the actinomycete mycelium in the studied soil samples (A horizon) are comparable to and the length of the viable fungal mycelium is lower than the analogous parameters recorded in forest soils of the temperate zone. It is noted that the viability of bacteria is close to that in forest soils of the temperate zone. The maximum concentration of soil biota is found in the A horizon of the studied soils, in contrast to forest biogeocenoses of the temperate zone, where soil biota is concentrated in the litter. It is shown for the first time that prokaryote communities are characterized by a significant presence of filterable forms of bacteria, the content of which increases in the series: soil (A horizon) → tree waste (dry leaves) → phylloplane (green leaves).

Relations between soil biota diversity and its contribution to the performance of some ecosystem functions were assessed based on the results obtained in undisturbed and burned spruce forests near the Central Forest Nature Biosphere Reserve (Tver oblast). In August 2014, in two 4-year-old burned areas, abiotic parameters of the soils, indicators of the state of the microbial communities, the number, taxonomic diversity, and the abundance of the main groups of soil invertebrates (testate amoebae, nematodes, enchytraeids, mites, collembolans, and the mesofauna as a whole) were determined. In the soils of the burned areas, higher CO 2 , CH 4 , and N 2 O emissions were observed. The number of bacterial cells remained similar, and the total length of active mycelium was not significantly different. All this implies a certain intensification of biogenic processes promoting the mobilization of carbon and nitrogen after fire. The number of most of the groups of soil animals was lower (not always significantly) in the burned area than that in the soils of the undisturbed forests. The changes in the taxonomic diversity were specific for each taxon studied. Overall, the diversity of invertebrates was related to the litter thickness. However, the high taxonomic diversity of soil fauna did not always correspond to the active functioning of the ecosystem. Thus, for some taxa, a quite close correlation was found, for instance, between the total number of species (of testate amoebae in particular) and the berry crop, as well as between the soil mesofauna population and the dead wood stock. The total diversity of the investigated taxa included in the detrital trophic web was the most reliable indicator of the carbon stock in the burned areas.

The diversity and viability of prokaryotic communities in the primitive organomineral soils of East Antarctica have been studied; it has been shown that the total number of bacteria is smaller than and the viability of bacteria is similar to that in soils of the temperate zone. The prokaryotic communities are characterized by the occurrence of a major part of cells in filterable forms, which is higher than the analogous parameter for the temperate soils. The method of fluorescence in situ hybridization (FISH) revealed that the distribution of the main taxons is similar to that in the temperate soils: the portion of the domain Archaea is smaller than that of the domain Bacteria; the total content of Gram-negative bacteria (the phyla Proteobacteria, Acidobacteria, and Planctomycetes) is higher than that of Gram-positive bacteria (Actinobacteria). Within the phylum Proteobacteria, a significant variation of three proteobacterial classes has been noted along the profiles of the soils studied.