Том 94, № 1 (2025)

In recent years, there has been an increasing interest of researchers in microorganisms capable of oxidizing higher gaseous homologues of methane (ethane, propane, n-butane). Among propane- and butane-oxidizing bacteria, representatives of Rhodococcus ruber attract special attention; they can easily adapt to extreme environmental conditions and have significant potential for biotechnology. The review emphasizes the importance of R. ruber as a bioindicator of oil and gas fields and a component of microbial consortia for the degradation of hydrocarbons and other xenobiotics. Data on natural substrates and ecological niches of gas-oxidizing Rhodococcus are presented, their morphological and physiological features are described. Their role in biogeochemical cycles and the potential for industrial use are discussed. As a result of the analysis of functional genes and enzyme systems of gaseous hydrocarbon (C₂−C₄) catabolism, the key stages of propane oxidation in Rhodococcus were identified and the role of propanotrophy in the bioremediation potential of R. ruber was revealed. The need for further research to understand the mechanisms of adaptation of these microorganisms to anthropogenic impact was substantiated.

Bacterial survival under unfavorable growth conditions is one of the fundamental problems of microbiology. The applied aspect of this problem – long-term preservation of bacterial cell viability – is of particular importance for storage of lactic acid bacteria due to the biotechnological significance of this group of microorganisms and their high rates of death during long-term storage. The aim of this study was to investigate the long-term survival of lactic acid bacteria of different physiological groups (heterofermentative Enterococcus faecium M3185 and homofermentative Lactobacillus paracasei AK 508) in silanol-humate gels (SHG) containing various organic acids used as titrants in obtaining SHG (malic, lactic, acetic, ascorbic, citric). Placing cells in CHG with organic acids resulted in a significant increase in the titer of viable cells relative to the control during long-term storage (up to 200 times) and depended on the bacterial culture, the acid used and the storage period (up to 5 months). The experimentally proven reasons for the long-term survival of bacteria in CHG are: 1) most of the cells are in a state of hypometabolism and consume organic acids, which is evidenced by a decrease in their concentration during storage, as well as by the release of CO₂ in the case of E. faecium (in this case, the metabolic rate is 1000 times lower than that of growing cells); 2) the absence of mass autolysis of cells, which is presumably due to the “disunity” of the cells in the gel and the impossibility of creating sufficient concentrations of autoregulators and autolysis enzymes; 3) some of the cells are in a state of rest, in the form of stress-resistant cyst-like cells. There is also reason to believe that when transferred to a gel, an alternative (biofilm) phenotype is formed, which has increased stress resistance. The results obtained indicate the feasibility of immobilizing lactic acid bacteria cells in SGG with organic acids for long-term storage.

Abstract. Field trials of rhizobial inoculants require simple and reliable methods for identifying the strains used to determine which strain has formed a nitrogen-fixing nodule. This task arises when testing the competitiveness of inoculant strains against local rhizobia strains, to track the fate of inoculant strains over long periods after the introduction of strains, and finally, such methods may be in demand when protecting the rights of strain owners and developers. The essence of the proposed identification method is to search for strain-specific DNA regions that are absent in other genomes of the same species and to construct a primer system for multiplex PCR, allowing simple, reliable and rapid identification of the strain. The advantages of this approach over other identification methods are, firstly, high reproducibility, and secondly, that the method is based on the detection of structural variants, the contribution of which to the evolution of rhizobia genomes is very high, while most genomic fingerprinting methods (AFLP, RAPD, REP, ERIC, etc.) are based on the detection of nucleotide polymorphisms in short fragments of the genome, but miss many events associated with genomic rearrangements and horizontal gene transfer. The use of the proposed method can also serve to monitor the evolutionary dynamics of rhizobial inoculant strains, especially in unique fragments of the genome, which is very important for R. leguminosarum, where the proportion of unique sequences is much higher than in other rhizobia.

Alas (thermokarst) basins with lakes are unique landscapes of the cryolithozone, widespread in the territory of Central Yakutia and traditionally used by the indigenous population for household needs (as sources of water, pastures and hayfields). In addition, alases are of great climatic importance, since they are active sources of greenhouse gas emissions. Microbial communities play a key role in the transformation of buried and modern organic matter entering alas ecosystems as a result of the impact of climatic and anthropogenic factors. However, microbiological studies of such ecosystems are extremely rare. This paper characterizes the phylogenetic diversity of microbial communities in the bottom sediments of three alas lakes in Central Yakutia – Tyungyulyu, Taby and Kharyyalakh. It was found that anaerobic chemoheterotrophic prokaryotes predominate in the sediments, but at the same time a large diversity of uncultured microorganisms with unknown metabolism was revealed. It is shown that microbial communities of bottom sediments can be indicators of agricultural load experienced by lakes. Microorganisms of the methane cycle were highly represented in the lake with the lowest anthropogenic load.

The microbiome of copepods of the genus Diaptomus from a high-altitude lake at Western Caucasus was investigated using 16S rRNA gene profiling. Aerobic and anaerobic organotrophic microorganisms, methanogenic archaea, and aerobic methane-oxidizing bacteria (MOB) constituted the basis of the microbiome. The symbionts and bacteria of the copepod diet were revealed. Anaerobic organotrophic microorganisms inhabiting the copepods provide the substrates for methanogens, the second most abundant physiological group of prokaryotes in the microbiome. Acetoclastic methanogens of the genus Methanothrix and hydrogenotrophic methanogens of the genera Methanobacterium and Methanoregula were predominant. The methane cycle within the copepods was closed, since their microbiome contained a diverse population of aerobic MOB, among which members of the genera Methylobacter and Methyloparacoccus (class Gammaproteobacteria) predominated. Methane exchange between methanogens and methanotrophs occurs probably in the anoxic environment of the copepod intestine under direct contact of the target microorganisms.

Biotechnologically significant strains of bacteria of the Pseudomonas genus have been isolated from the rhizosphere of wild and cultivated cereals. The isolated strains are able to biocontrol the phytopathogenic fungi and bacteria and degrade the herbicide glyphosate as the only source of phosphorus (P. chlororaphis subsp. chlororaphis G16, P. chlororaphis subsp. aureofaciens G27, P. protegens G23-4) and the herbicide Axial as the only carbon source (P. chlororaphis G27). These strains exhibit lipolytic and proteolytic activities and P. chlororaphis G27 can also produce hydrogen cyanide, which has an antifungal effect. The studied strains can be useful as the basis of biopreparations for protecting plants from phytopathogenic microorganisms and treating soils polluted with herbicides.