Sergey Anatoljevich Potapov

The light spectrum is a key factor in aquaculture, but its effects on molecular stress responses during early fish development are unclear. This study examined how light of different wavelengths (spectra) affects embryos of Baikal whitefish Coregonus baicalensis and its hybrid with Yenisei hump-snout whitefish C. fluviatilis. Eggs were incubated from 35 days post-fertilization under white light (1.8 and 20 µmol m⁻² s⁻¹), darkness, red (peak at 631 nm), green (peak at 507 nm) and blue (peak at 459 nm) light. We analyzed relative telomere length, telomerase activity, blood profiles, and expression of stress-related genes (HSP-90, MtCK) at key developmental stages. Notably, a significant increase in telomere length was observed throughout early development (from embryo to larva to fry), independent of the light spectrum. Red light and darkness acted as potent stressors, indicating proteotoxic stress and energy imbalance. In Baikal whitefish, this was accompanied by notable telomere shortening at the earliest stage and elongation at later stages under certain conditions, potentially mediated by increased telomerase activity, a response that may be metabolically costly. Conversely, green light was the most neutral. The effect of blue light differed between Baikal whitefish and its hybrid, with the hybrid proving more sensitive. Furthermore, high-intensity white light (20 µmol m⁻² s⁻¹) also induced negative effects in the hybrid, such as increased telomere length, suggesting that excessive irradiance itself can be a stressor, independent of spectral composition. We conclude that darkness or a predominance of red light is suboptimal for incubating these whitefish, while green light provides a more favorable environment, offering a basis for optimizing aquaculture light conditions.

Cyanobacteria of the genus Tychonema are common inhabitants of freshwater bodies in a temperate zones. In Lake Baikal, Tychonema sp. was first reported in 2014. It grows excessively on the bottom on almost all substrates types, forming epiphytic and epizoic biofilms, and its role in the mass mortality events affecting of endemic Baikal sponges is discussed. The cyanobacterial strain BBK16 (=IPPAS B-2063^T), isolated from a biofilm on a log pier in the Bolshiye Koty settlement in 2016, was used for further taxonomic characterization. Key morphological features of strain BBK16 include its growth as a creeping mat, highly motile trichomes that are sometimes narrowed and hooked at the ends, and the presence of rounded-conical apical cells with a calyptra. Strain ultrastructure (fascicular parietal thylakoids and type D cell division) differs from Tychonema species with radial thylakoids but aligns with other genera in the Microcoleaceae family. A comprehensive analysis, including 16S rRNA gene phylogeny, conserved protein phylogeny, and whole-genome comparisons, confirmed its placement within the genus Tychonema. The average nucleotide identity, average amino acid identity and digital DNA–DNA hybridization values between strain BBK16 and T. bourrellyi FEM GT703 were 90.7%, 91.1% and 43.3%, respectively, indicating values below the standard thresholds for species delineation. Based on combined morphological, genomic, and ecological evidence, we propose the name Tychonema litorale sp. nov. for strain BBK16, a novel species described in accordance with the International Code of Nomenclature for Algae, Fungi, and Plants.

Understanding the molecular mechanisms that enable vertebrate adaptation to deep-water environments remains a central goal in evolutionary biology. This study used comparative transcriptomics of skeletal muscle tissue to investigate these mechanisms in four endemic sculpin fish species (Cottoidei) from Lake Baikal, which inhabit different depth niches ranging from pelagic to benthic-abyssal zones up to 1642 m. Pelagic species showed increased activity in genes involved in sarcomere structure, calcium handling, and motor proteins, indicating adaptations for sustained locomotion. In contrast, deep-benthic specialists showed enrichment in pathways for glycolytic metabolism, proteasome function, and ubiquitination, reflecting adaptations for energy efficiency and protein homeostasis in a high-pressure environment. We conclude that the colonization of the Baikal abyssal zone by sculpins relies on a suite of shared molecular mechanisms, with distinct ecological pressures driving specific transcriptional changes in motility, metabolic strategy, and cellular integrity. This study provides a systems-level model for deep-water adaptation in vertebrates.

Microcystis, a potentially toxigenic cyanobacterium known to form extensive blooms in eutrophic lakes globally, was investigated in the cold oligotrophic Lake Baikal. We report the isolation of two Microcystis strains, Microcystis aeruginosa and M. novacekii, and document the presence of the latter species in Lake Baikal for the first time. In M. aeruginosa strain BN23, we detected the microcystin synthetase gene mcyE. Liquid chromatography-mass spectrometry revealed the presence of two microcystin variants in BN23, with microcystin-LR, a highly potent toxin, being the dominant form. The concentration of MC-LR reached 540 µg/g dry weight. In contrast, M. novacekii strain BT23 lacked both microcystin synthesis genes and detectable toxins. The habitat waters were characterized as oligotrophic with minor elements of mesotrophy, exhibiting low phytoplankton biomass dominated by the chrysophyte Dinobryon cylindricum (76–77% of biomass), with cyanobacteria contributing 8–10%. The contribution of Microcystis spp. to the total phytoplankton biomass could not be quantified as they were exclusively found in net samples. The water temperature at both sampling stations was ~19 °C, which is considerably lower than optimal for Microcystis spp. and potentially conducive to enhanced microcystin production in toxigenic genotypes.

Metabarcoding research of the domestic animal intestines is relevant for veterinary medicine. The effect of feeding and food additives on its gut microbiome is of both applied and fundamental significance and demonstrates the stimulation of the various groups of bacteria development. The objective of our work is to study the effect of the domestic complete pet feed Dilly on the microbial community of the dogs’ intestines in breeding kennel of Irkutsk. The microbiome composition was determined in 12 animals of different ages having used Illumina MiSeq amplicon sequencing of the V3-V4 region of 16S rRNA. Rates diversity had been adapted to evaluate the affluence and prominence of Bacterial operational and taxonomic units and nonparametric Mann-Whitney criteria (correlative test, p≤0,05) used to evaluate the certainty value of the difference of operational and taxonomic unit percentage in different physiological groups. All in all, 147150 the 16S rRNA gene fragment sequences were obtained. The dominant bacteria turned out to be the phyla Firmicutes, Actinobacteriota, Bacteroidota, and Proteobacteria. The animals that had been under research had almost no Fusobacteriota bacteria - markers of a diet with a predominance of raw meat (predation). The Firmicutes phylum included bacteria from five families. The most numerous families among the Firmicutes were the Lactobacillaceae bacteria. Representatives of seven families were observed among Actinobacteriota bacteria, of which Bifidobacteriaceae predominated. Proteobacteria of the Enterobacterales order and Burkholderiales made up a small proportion of the entire community and depended on the animal age. The research result could be used in perspective to enlarge knowledge about the digestive process in an omnivorous animal of the wolf pack. These animals have a more or less flexible microbiome, which has several variants of normal composition. There predominated lactic acid bacteria in the microbial communities of the dogs’ intestines, which consumed feed that contained coarse dietary fibers. In its turn, lactic acid bacteria reduced the number of Fusobacteriota.

In this work, we describe the transcriptional profiles of preadapted and non-adapted one-month-old juvenile Baikal whitefish after heat shock exposure. Preadapted fish were exposed to a repeated thermal rise of 6 °C above the control temperature every three days throughout their embryonic development. One month after hatching, preadapted and non-adapted larvae were either kept at control temperatures (12 °C) or exposed to an acute thermal stress (TS) of 12 °C above the control temperature. In response to this acute stress, an increase in HSP gene expression (HSP-30, HSP-40, HSP-47, HSP-70, and HSP-90) and TRIM16 was detected, independent of preadaptation. The expression levels of genes responsible for the response to oxygen levels, growth factors and the immune response, HBA, HBB, Myosin VI, Myosin VII, MHC, Plumieribetin, TnI, CYP450, and LDB3 were higher in individuals that had previously undergone adaptation. Genes responsible for the regulation of metabolism, MtCK, aFGF, ARF, CRYGB, and D-DT, however, increased their activity in non-adapted individuals. This information on transcriptional profiles will contribute to further understanding of the mechanisms of adaptation of whitefish to their environment.

Acclimation through the hormesis effect increases the plasticity of organisms, which has been shown for many ectothermic animals, including fish. We investigated the effect of temperature acclimation in Baikal whitefish Coregonus baicalensis (Dybowski, 1874). Telomere length, telomerase activity, and the expression of genes, whose products are involved in the regulation of telomere length and defense against reactive oxygen species, were selected to assess the state of the larvae. Acclimation and acute temperature stress (+12 °C) had no effect on telomere length, but altered telomerase activity (acclimation decreased it; stress increased it) and the levels of genes expression. Under stress, the expression of superoxide dismutase genes was increased in acclimated larvae and that of glutathione peroxidases in non-acclimated larvae, which may indicate lower reactive oxygen species formation and slower antioxidant responses in acclimated fish. The expression of some telomere-related genes was reduced under temperature stress, but the expression of the tzap and smg genes, whose products improve the control of telomere length by preventing them from lengthening or shortening, was increased in acclimated individuals. The data obtained indicate a positive effect of acclimation on the state of the Baikal whitefish larvae by remodulation of their telomerase activity and the transcriptional profile.

The work deals with investigation of genetic diversity and biogeography of T4-like cyanophages from the shallow bay of the Posolsky Sor (Lake Baikal), based on analysis of the g20 marker gene. High diversity of the g20 gene fragments and their uniqueness were revealed. The greatest similarity was noted with the previously obtained sequences from Lake Baikal and with those from freshwater ecosystems: oligotrophic Lake Green, Lake Round, oligomesotrophic Lake Annecy, and mesotrophic Lake Bourget. From the point of view of biogeography, it was determined that the phage sequences were more similar to the previously obtained ones from different Lake Baikal ecotopes than to those from other ecosystems.