P. A. Kozhevin

Soil actinomycetes as potential biofungicides

The biological control of fungal diseases in plants is considered an efficient and environmentally friendly alternative or supplement to fungicides. Soil antagonistic streptomycetes are particularly suitable for the biological control; they proved to be highly efficient in reducing the incidence of fungal pathogens. Streptomycetes isolated from the podzolic soils were evaluated for the biosuppression of fungal populations. Seventeen strains of streptomycetes (out of the total 279 isolates) were found to be strongly antagonistic to fungal pathogens in vitro and were selected for further experiments in situ. The full protection of plants against Fusarium spp. was obtained with the Streptomyces hygroscopicus strain K49.

Optimization of natural communities of soil microorganisms as a way to create microbial fertilizers

We have shown that it is possible to obtain complex microbial fertilizers for different purposes based on microbial communities without growing microorganisms on nutrient media. Control of the natural microbial community may be carried out using the methods of mathematical experimental design in the course of microbial successions.

Filamentous actinobacteria of the saline soils of arid territories

A large number of actinomycetes (hundreds, thousands, and millions of CFU/g of soil) were isolated from saline soils in the territory of the landscapes of the Ber hillocks. A significantly smaller quantity of actinomycetes was isolated from the soda saline soils and sor saline soils that formed at the bottom of the ephemeral salty lakes in Buryatiya and in the estuary of the Syr-Darya River. Actinomycetes were represented in the studied soils by the Streptomyces, Micromonospora, Actinomadura, and Nocardiopsis genera. Among streptomycetes, the species of the Albus section and the Albus series predominated. The activity of the consumption of substrates by cultures of actinomycetes was largely influenced by conditions of preincubation. Obviously, the influence was related to the alteration in the metabolism of actinomycetes as one of the mechanisms of adaptation to the increased osmolarity of environment. The alcalotolerance, thermotolerance, and xerotolerance of halotolerant actinomycetes of the saline soils of arid territories were experimentally revealed.

Absolute number of Bacteria and Archaea in soil

The possibility of using the method of exhaustion (removal sampling) applied to determine the absolute number of Bacteria and Archaea populations in soil based on accounting data for quantitative fluorescence in situ hybridization has been shown.

Natural functions of antibiotics as “informbiotics”

The discovery of antibiotics is one of the main achievements in the science of 20th century. However, the question about their natural functions is still unsolved. Recently, the necessity for the transition from the anthropocentric view on antibiotics (destruction of other organisms) to analysis of their signal role in the processes of “fine tuning” was realized. The characteristics of the current state of knowledge about antibiotic functions in natural conditions are given in the present review.

The soil antibiotic resistome

Antibiotic resistance of pathogenic microorganisms is considered to be an important and urgent public health problem. Rapid and large-scale development of antibiotic resistance at a global level actually means a return to the pre-antibiotic age. The soil resistome conception includes all genetic components of antibiotic resistance that are present in a given natural microbial community. Soil (as a natural habitat) is a reservoir of resistant microorganisms and contains corresponding genetic information about antibiotic resistance.

Specificity of soil hydrolytically microbial complex under different moisture conditions

It has been established that soil moisture has a significant impact on the activity of chitinolytic microbial processes, rather than pectinolytic processes. The degradation of polysaccharides with an increase in soil moisture in microbial complex markedly increases the role of prokaryotic microorganisms, especially actinomycetes. For the first time, using the FISH method, the amount of detected phylogenetic composition of a metabolically active hydrolytic complex of humus horizons of grey forest and gley and weakly podzolic soil and humus has been estimated depending on the humidity. At optimum moisture, phylogenetic groups Actinobacteria and Firmicutes dominated in the chitinolytic process. An increase in the proportion of proteobacteria is observed with an increase in humidity. The role of gamma- and alphaproteobacteria and actino-bacteria is heightened with the drying of soil in the hydrolytic complex. A quantitative estimate of the rate of degradation of polysaccharides (pectin and chitin) in different types of soils at different levels of moisture is given. The dependence of the phylogenetic composition of an active microbial hydrolytic complex of humus horizons of grey forest and gley, weakly podzolic soils and humus on humidity is revealed.

Temperature as a factor of development of psychrotolerant mycelial bacteria complexes in soils of north regions

It has been demonstrated that complexes of mycelial bacteria (actinomycetes), in which the amount of psychrotolerant actinomycetes reaches hundreds of thousands of CFU/g of the soil (frequently exceeding the portion of mesophilic forms), are developed in peat and podzolic soils of the tundra and taiga at low temperatures. As actinomycetes grow and develop in cold soils, their mycelium increases in length. Use of the molecular in situ hybridization method (fluorescent in situ hybridization, FISH) demonstrated that the portion of metabolically active mycelial actinobacteria exceeds the portion of unicellular actinobacteria in the Actinobacteria phylum. Specific peculiarities of psychrotolerant populations in relation to the spectrum of consumed substrates (histidine, mannitol, saccharose) were established by the method of multirespirometric testing.

Soil management for agro-ecosystems

Several problems of soil biotechnology and their relation with global ecological problems are considered. An analysis of the principal opportunities for soil biota management shows that scientific progress in this field is a necessary but insufficient condition for the solution of these global problems.

The role of soil microorganisms in environmental and food security

The review considers some problems of soil microbial system management, as well as the possibilities, constraints, and risks caused by environmental and food security problems. A natural microbial system, which obeys its own dynamic laws, is considered a required condition for the existence of a biosphere. Ignorance and disregard of these laws can lead to catastrophic consequences for the higher hierarchical system in which humanity acts.