— Molecular biology techniques have been applied to study the diversity and biomass of metabolically active prokaryotic cells in an oil-contaminated oligotrophic peat soil at different levels of mineral nutrition. The share of metabolically active components in the peat samples is only about 10% of the entire prokaryotic community. The application of mineral fertilizer (N 40 P 50 K 50 ) against the background of half-dose liming has led to a more than twofold increase in the biomass of bacterial and archaeal cells, an increase in the number of functional genes ( bss and nifH ) copies, and a significant decrease in the content of oil products in the peat of experimental variants. The application of mineral fertilizer against the background liming of oil-to contaminated soil induces changes in the phylogenetic structure and partial restoration of the metabolically active prokaryotic complex.

Molecular genetic techniques (FISH and metabarcoding) were used to investigate comparative biodiversity in the prokaryotic complex of soil microcosms of gray forest, chestnut, and chernozem soils before and after oil pollution. At the level of high-rank taxonomic units, the structure of prokaryotic communities from different soil types was similar. In oil-polluted microcosms microbial diversity decreased, and the metbolically active dominants of the Bacteria and Archaea domains changed compared to the control samples. A specific bacterial complex was found to emerge in experimental samples of all soil types, with predominance of the Gammaproteobacteria and Actinobacteria, as well as of archaea, among which Thaumarchaeota and Crenarchaeota prevailed. Members of the soil prokaryotic complex active and inactive in respect to oil pollution were determined. Our results indicate similar succession responses of microbial communities from different soil type to oil pollution.

Actinomycetic complexes of soils and plant substrates from tundra and taiga zones of Russia and Finland have been studied. A molecular cytogenetic technique—fluorescence in situ hybridization (FISH) method—has been applied to estimate the metabolically active component in the representatives of the Actinobacteria. In the prokaryotic microbial communities of studied plant substrates, the biomass of metabolically active psychrotolerant representatives of Actinobacteria was determined upon incubation at 5°C reached 34% of the total bacterial biomass; at the incubation temperature of 20°C, it increased to 56%. Under conditions of low temperature, psychrotolerant actinomycetes displayed active growth with the development of both substrate and aerial mycelium. The abundance of psychrotolerant actinomycetes reached thousands and tens of thousands CFU/g for taiga mosses in Finland and increased to millions CFU/g for tundra flowering plants in the Taimyr Peninsula of Russia. It decreased in the sequence: peat soil > plants > moss cushions > litter horizons. The length of actinomycetic mycelium in tundra plants varied from 98 m/g at 5°C to 291 m/g at 20°C; in taiga mosses, it varied from 120 to 180 m/g, respectively. The complex of psychrotolerant actinomycetes was mainly composed of colorless species of the Streptomyces genus possessing specific ecophysiological features, such as the change in the color of substrate and aerial mycelium, the appearance of pigmentation, and the increase in the growth rate upon higher incubation temperatures. More than 60% of actinomycetes isolated from taiga mosses of Finland were represented by psychrotolerant species of Micromonospora genus.

Application of molecular biological techniques in environmental studies provides a more complete information concerning the taxonomic diversity and potential hydrolytic activity of soil microbial complexes that exist in a wide range of environmental factors. Among the key environmental parameters that determine the functional activity of the hydrolytic complex of soil layer, the most significant one is moisture. Moisture levels providing maximum activity of a hydrolytic microbial complex depend on the soil type. At high levels of moisture and temperature, the role of prokaryotic organisms, mainly actinomycetes, in the microbial complex significantly increases. It was discovered a new functional activity of actinomycetes in the hydrolytic prokaryotic complex: their controlling influence on the respiratory level of the complex in a wide range of parameters (moisture, organic matter, successional time).At the optimum for the life of most microorganisms levels of moisture (60% of field capacity) and temperature (27°C), representatives of Firmicutes and Actinobacteria phylums stand out among chitinolytic and pectinolytic dominants of the studied soils within the Bacteria domain. With increasing moisture and decreasing temperature the proportion of Proteobacteria increases. With decreasing moisture and increasing temperature, there is an increase in the amount of unicellular actinobacteria.

Studies of tundra flowering plants and mosses on the Тaymyr Peninsula have determined the presence of thousands and tens of thousands of colony formation units of psychrotolerant actinomycetes in 1 g of vegetation substrate, which is smaller than the amount of mesophilic forms by one to two orders of magnitude. Incubation of plants at 5°C has shown very small taxonomical variety of actinomycetes. The actinomycete complex is represented by species of the genus Streptomyces , belonging to the sections and series Albus Albus and Cinereus Achromogenes , and by the genus Micromonospora .

Associations of cyanobacteria with actinomycetes are not investigated. The task was set in this work to study the biological aspects of coexistence of free-living cyanobacterium Anabaena variabilis with actinomycetes isolated from corraloid roots of Strangeria eriopus и Cycas micho- litzii and cyanobacterium Oscillatoria terebriformis (Ag.) Elenk. emend., which were isolated from the natural cyano-bacterial mat of Kamchatkan thermal spring, with actinomycetes, isolated from accumulating culture of cyanobacterium. Positive tropism of streptomycetes hyphes to the cya- nobacterial trichoms and cyanobacterium to streptomycetes were observed. Stimulation of growth of O. terebriformis in the associated culture with the streptomycete was marked. The increase of the fixation of nitrogen by A. variabilis and of photosynthetic activity by O. terebriformis in the associated culture with the streptomycete was marked. On this background associative interaction cyanobacteria with streptomycetes are positively discussing.

The population density of actinomycetes in the samples of light sierozem from the Kopet Dag piedmont plain (75 km from Ashkhabad, Turkmenistan) reaches hundreds of thousand CFU/g soil. The actinomycetal complex is represented by two genera: Streptomyces and Micromonospora . Representatives of the Streptomyces genus predominate and comprise 73 to 87% of the actinomycetal complex. In one sample, representatives of the Micromonospora genus predominated in the complex (75%). The Streptomyces genus in the studied soil samples is represented by the species from several sections and series: the species of section Helvolo-Flavus series Helvolus represent the dominant component of the streptomycetal complex; their portion is up to 77% of all isolated actinomycetes. The species of other sections and series are much less abundant. Thus, the percentage of the Cinereus Achromogenes section in the actinomycetal complex does not exceed 28%; representatives of the Albus section Albus series, Roseus section Lavendulae-Roseus series, and Imperfectus section belong to rare species; they have been isolated not from all the studied samples of light sierozem, and their portion does not exceed 10% of the actinomycetal complex.

Ecological and taxonomic characteristics of the actinomycete complex of solonchak soils and light chestnut soils in the Lake Elton region have been presented. Data on the abundance and taxonomic structure have confirmed the ecological importance of actinomycetes in soils with evident signs of salinity.

В настоящем обзоре приведены результаты многолетних исследований сотрудников кафедры биологии почв факультета почвоведения МГУ, связанные с изучением одной из главных функций почвенных микроорганизмов – осуществление и поддержание круговорота веществ и энергии в биосфере. Приведены данные по численности и запасам микробной биомассы в разных типах почв, проанализированы результаты системного подхода к изучению структурно-функциональной организации микробных сообществ почв, показана роль эукариотных и прокариотных микроорганизмов в циклах углерода и азота. Для осуществления круговорота химических элементов в наземных экосистемах требуются высокая численность и разнообразие форм микроорганизмов, но при этом встает вопрос о сохранении микробов в почвах в жизнеспособном состоянии. Приведены новые данные об одном из способов переживания бактерий в почвах в виде наноформ; рассмотрены такие природные банки микроорганизмов, как торфяники и палеопочвы, в которых микробы могут сохраняться в течение десятков тысяч лет.

The results of long-term investigations performed by researchers from the Department of Soil Biology at the Faculty of Soil Science of Moscow State University into one of the major functions of soil microorganisms—sustenance of the turnover of matter and energy in the biosphere—are discussed. Data on the population densities of soil microbes and on the microbial biomass in different types of soils are presented. The systemic approach has been applied to study the structural-functional organization of the soil microbial communities. The role of eukaryotic and prokaryotic microorganisms in the carbon and nitrogen cycles is elucidated. It is argued that the high population density and diversity of microorganisms are necessary to maintain the turnover of chemical elements in terrestrial ecosystems. The viability of microbes stored in the soils is important. New data on the preservation and survival of bacteria in nanoforms are presented. It is shown that peatlands and paleosols are natural banks, where microbes can be preserved in a viable state for tens of thousands years.

Установлена высокая численность (до сотен тысяч и миллионов КОЕ/г почвы) мицелиальных бактерий (актиномицетов), выделяемых из засоленных почв аридных территорий Украины, России, Туркменистана. Среди всех изученных почв достоверно меньшее (тысячи и десятки тысяч КОЕ/г почвы) количество актиномицетов выделяется из соровых и содовых солончаков, формирующихся на дне пересыхащих соленых озер в Бурятии и в дельте Аму-Дарьи. Актиномицеты представлены в исследуемых почвах родами Streptomyces, Micromonospora, Nocardiopsis. Выявлено, что на активность потребления субстратов культурами актиномицетов в значительной степени влияют условия предынкубирования, что, очевидно, связано с перестройкой метаболизма актиномицетов как одного из механизмов адаптации к повышенной осмолярности среды. Экспериментально установлена алкалотолерантность галотолерантных актиномицетов, выделенных из почв засоленных территорий.

A high population density (up to hundreds of thousands or millions CFU/g soil) of mycelial bacteria (actinomycetes) is determined in salt-affected soils of arid territories of Ukraine, Russia, and Turkmenistan. Of all the studied soils, the lowest amounts of actinomycetes (thousands and tens of thousands CFU/g soil) are isolated from sor (playa) and soda solonchaks developed on the bottoms of drying salt lakes in Buryatia and in the Amu Darya Delta. Actinomycetes of the Streptomyces, Micromonospora , and Nocardiopsis genera were recorded in the studied soils. It is found that conditions of preincubation greatly affect the activity of substrate consumption by the cultures of actinomycetes. This could be attributed to changes in the metabolism of actinomycetes as a mechanism of their adaptation to the increased osmotic pressure of the medium. The alkali tolerance of halotolerant actinomycetes isolated from the salt-affected soils is experimentally proved.