Tatyana Alexandrovna Gracheva
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Bacterial complexes in the fens of Tomsk region: abundance, taxonomic structure, activityMoscow University Bulletin. Series 17. Soil science. 4. p.43-51read more581
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This article provides an analysis of structural and functional indicators of bacterial complexes taken for examination from the complete profile of the fens that form part of “Klukvennoye” and “Karbyshevskoye” wetland systems in the Tomsk Region. In the fens bacteria was found throughout all the profile. The number of bacteria was high and varied from 27 to 78 ´ 109 cells/g of dry peat. This data was obtained by direct method using fluorescence microscopy. The high count of the saprotrophic bacteria (reaching up to 108-109 CFU/g of dry peat) was found by the plate method. Those results allowed to identify a trend, showing that the number of saprotrophic bacteria increased down the fen profile. The results of this study give an opportunity to state for the first time that the index k ( k is a dimensionless universal characteristic of natural prokaryotic communities, k stands for microscopy/plate) in fen profiles does not increase, but decreases with depth. The following bacterial cultures were identified and isolated from the fens studied (those cultures were attributed to 10 taxa): Bacillus, Streptomyces, Arthrobacter, Microbacterium, Pseudomonas, Pedobacter, Flavobacterium, Dyadobacter, Janthinobacterium, Myxobacteriales. Bacterial cultures, representing Bacillus and Streptomyces genera, were dominant in the acrotelm. At the same time Pseudo-monas, Dyadobacter and Arthrobacter dominated in the catotelm. The functions of bacterial genera and species, identified by molecular biological methods, were described. A study of nitogen fixation, nitrogen decline and methanogenesis showed that bacteria were in a viable state and were able to remain active throughout the entire peat profile.
Keywords: fens; Sapric Histosols; bacteria; abundance; taxonomic structure; nitrogen fixation; denitrification; methanogenesis
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The influence of erodibility degree of sod-podzolic soil on the abundance and diversity of fungi and actinomycetesMoscow University Bulletin. Series 17. Soil science. 2024. 3. p.28-37Valery V. Demidov Tatyana A. Gracheva Polina M. Perebasova Alla V. Golovchenko Alexey L. Stepanov Oleg A. Makarovread more248
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The paper presents the results of assessing the eff ect of the degree of soil erodibility on the abundance and diversity of cultivated fungi and actinomycetes in diff erent seasons of the annual cycle. The objects of the study are sod—podzolic soils (Umbric Retisols (Abruptic)) of diff erent degrees of washout, located on the slope of the southeastern exposure (Moscow region, Solnechnogorsk district), used for a long time for the cultivation of agricultural crops. The indicators of microbial abundance were determined by the cup method, identifi cation was carried out on the basis of phenotypic characters. It is shown that the decline in physical and agrochemical parameters of the soil, which is a result of erosion processes, leads to a change in microbiological parameters. A decrease in the abundance and species diversity of fungi and actinomycetes was found with an increase in the degree of soil erosion. Significant diff erences were found in the taxonomic composition of microbial communities of non-eroded and washed away soils (the Sorensen species similarity coeffi cient does not exceed 0.42 for fungi and 0.30 for actinomycetes). Taxonomic units of mycelial microorganisms have been identifi ed. Among the fungi are representatives of the species Aspergillus, Cladosporium and Scopulariopsis, among the actinomycetes are Streptomyces malachitospinus, S. candidus and Micromonospora aurantiaca.Keywords: water erosion; erodibility; abundance; indicator species
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