Microbiology

Since the early 60s of the 20th century, as a result of agricultural development in the irrigated areas of Uzbekistan, the area of the Aral Sea has decreased by 90%, while the water salinity has increased from 1% to 20%. The aim of our work was to investigate the diversity of microbial communities of water and sediments of the Western Aral Sea, as well as of the adjacent soils and reservoirs using high-throughput sequencing of the 16S rRNA genes variable V4 region. It was found that the Aral Sea water with a salinity of 22% was dominated by uncultured Archaea of the family Haloferacaceae (22‒43%), as well as by bacteria of the genera Spiribacter and Psychroflexus. In the Aral Sea sediments the share of archaea was much lower (2‒17%), and among them the uncultured Woesearchaeales predominated. Among bacteria, dominating in Aral sediments, there were sulfate reducers of the phylum ‘Desulfobacterota’, as well as representatives of the genera Fusibacter, Halanaerobium, Guyparkeria, Marinobacter, Idiomarina and Thiomicrospira. In soil samples of the former Aral Sea bed with salinity of 8.2%, a variety of archaea of the phylum Halobacterota were present, as well as uncultured bacteria of the family Nitrosococcaceae. However, in the rhizosphere of Ewresmann’s teresken plant (Kraschennininikovia ewresmanniana) growing there, archaea accounted for only 4% and mainly represented the family Nitrososphearaceae. 33% of all prokaryotes in the rhizosphere microbiome were the uncultured representatives of the phylum Actinomycetota. The microbial community of the teresken rhizosphere turned out to be similar to the microbial communities of the soil of the Ustyurt plateau, located in 3 km from the Aral Sea shore. The fresh water flowing along the former Aral Sea bed from an artificially drilled well also causes significant changes in the microbial communities: cyanobacterial mats and associated organotrophic bacteria develop along the stream bed with the increasing salinity (0.5‒2%). Finally, the greatest diversity of prokaryotes was found in the microbial community of Sudochie Lake sediment with salinity of 1%, which is probably a modern analogue of the Aral Sea microbiome before its shallowing.

Halophilic and halotolerant microorganisms have a high biotechnological potential. They are producers of biologically active substances, stress-protective agents, hydrolytic enzymes, and are used for environmental bioremediation. At the same time, the characterization of novel halotolerant bacteria and the disclosure of their salt tolerance strategy are topical fundamental problems. In the present work, a new strain MX2 was isolated from the salt well brine of the Yakshinskoe potassium-magnesium salt deposit. The isolate is represented by aerobic gram-positive non-motile bacteria that do not produce spores. The cell morphology varies from cocci to short rods that are capable of producing V-shaped forms. Colonies on the surface of agar nutrient medium were circular with an entire edge and raised center, glistening and orange. Bacteria of strain MX2 are halotolerant microorganisms capable of growing at NaCl concentrations up to 9%. Strain MX2 was sequenced. Its size was estimated at 3747717 b. p., the number of protein-coding genes — 3562. Strain MX2 was identified as belonging to the species Dietzia maris based on analysis of 16S rRNA, gyrB, rpoB, recA, ppk gene sequences and using time-of-flight mass spectrometry (MALDI-TOF-MS). D. maris MX2 has complete metabolic pathways for the synthesis of ectoine, hydroxyectoine, and trehalose, as well as transport systems for ectoine, hydroxyectoine, trehalose, glycerol, glycerol-3-phosphate, L-proline, and glycine-betaine. Thus, to ensure the osmotic balance, D. maris MX2 uses the strategy of accumulating compatible organic solutes.

The effect of hydrocarbon pollution on the fungal communities of littoral sediments of the cold-water White and Barents seas was investigated. The samples were collected at locations with different levels of pollution with oil products, from ports to relatively undisturbed areas. Using the diesel fuel-containing medium resulted in detection of hydrocarbon-degrading fungi in almost all studied samples, although in all cases they were less diverse than sugar-degrading fungi. In this relatively small group, Penicillium chrysogenum and Penicillium brevicompactum were the most common organisms. Fungal communities isolated on a sugar-containing medium exhibited higher diversity and abundance, with being the most common sugar degraders. The major factors affecting the structure of the fungal communities were the percentage of hydrocarbons in the total mass of organic carbon in the samples in the case of hydrocarbon-degrading fungi and location, for sugar degraders. In the experiment, the highest hydrocarbon-degrading activity was shown for Penicillium chrysogenum (the loss of residual hydrocarbons was 77.4%), Cadophora fastigiata (72%), and Tolypocladium inflatum (67.2%).

The structure of micromycete communities in the library aerial environment was investigated in 57 Russian cities located in seven federal districts (Northwestern, Central, Southern, Volga, Ural, Siberian, and Far Eastern). A total of 107 micromycete species belonging to 41 genera were isolated and identified. Due to mostly similar conditions, the aerial ecosystem of internal spaces of the library storage facilities was relatively stable, with moderate diversity and high evenness, as was confirmed by the relevant indices: the Shannon index varied from 2.7 to 3.4, the McIntosh diversity index, from 22.7 to 140.8, and the Menhinick index, from 2.1 to 3.0. The Simpson’s dominance index and the Berger–Parker index did not exceed 0.11 and 0.24, respectively. The McIntosh and Pielou’s evenness indices were 0.71–0.78 and 0.79–0.85, respectively. High similarity of the taxonomic structures, independent of climatic conditions of the studied regions, was revealed, as was confirmed by the values of the Stugren–Radulescu and Morisita–Horn coefficients: 0.08‒0.77 and 0.04‒0.47, respectively. The typical members of the studied mycobiota were Aspergillus versicolor (7.5‒14.3), Cladosporium cladosporioides (17.5‒40.5), C. herbarum (0.8‒53.6), and Penicillium aurantiogriseum (6.5‒32.4). Most other species were scarce, with frequencies of occurrence not exceeding 7.1%.

A significant part of research in environmentally friendly agroindustrial production is aimed at immobilized bacterial preparations with retained capacity for active growth without loss of metabolic activity both during immobilization and after long-term storage and biotechnological use. In the present work, immobilization of members of the genus Azospirillum on natural and synthetic carriers was investigated. Efficiency of immobilization of the cells of A. brasilense strain SR80 in alginate hydrogel and vermiculite was investigated. Proliferative and metabolic activities of immobilized preparations were investigated. The prospects of using vermiculite and calcium alginate as matrices for Azospirillum immobilization are shown.