Objective: to study the evolution of SARS-CoV-2 virus in the process of adapting to human organism duringthe current pandemic.Materials and methods. Database (GISAID) on nucleotide sequences of SARS-CoV-2 virus genome, obtained from clinical samples during the period of late December, 2019–July, 2020. Phylogenetic tree diagram construction was carried out applying BioNumerics v.7.6 software using Maximum parsimony algorithm.Results and discussion. The most substantial change in the genomes of SARS-CoV-2 virus are associated one-time mutations in ORF1b (P314L) and S (D614G) genes, as a result of which the overwhelming majority of identified isolates of this virus have the stated pair of substitutions to date. Many researches link the substitution in S (D614G) gene to the decreased pathogenicity in the strains that contain it, which may be also explained by enhanced methodology of patient treatment in the course of pandemic. The effect of the mutation in ORF1b (P314L) gene has not yet been investigated. P314L and D614G mutations are closely related and only their combined presence in the genome favored the dissemination of the genovariants of SARS-CoV-2 virus. Analysis of congregated epidemiological data testifies to the fact that the spread of new genovariants may be associated with biological properties facilitating human-to-human transmission. Thereat, associated decrease in lethality may reflect not only advancements in methods of treatment, but possible attenuation of virulent properties. Thus, observed growth in dissemination potential against the background of decrease in virulence is, probably, one of the forms of adaptation of new coronavirus to human population and, apparently, will remain in the future as the integration of SARS-CoV-2 virus into the structure of seasonal ARVI agents.

Objective of the study was to identify the differences in the production of proteins in typical strain and genetically altered variant of V. cholerae O1, biovar El Tor.Materials and methods. Natural strains M1062 (Astrakhan, 1970) and M1509 (Moscow, 2010) were used as model strains in this work. Strains were cultivated on Luria Bertani agar at 37 °C. Electrophoresis was performed in accordance with W.K. Laemmli technique (1970), mass-spectrometric profiling – the method described by A. Shevchenko et al.Results and discussion. Mass-spectrometric scanning of cell lysates of the examined strains showed significant similarity of their proteomes (615 common proteins). The identified differences pertained to high expression of proteins in the strain M1062, participating in biosynthesis of DNA/RNA, included into “purines, pyrimidines, nucleosides” group, as well as regulatory proteins. In M1509 strain, biosynthesis of the proteins responsible for pathogenesis, adaptation under the influence of unfavorable environmental factors, included into “co-factors, vitamins, pigments” group, involved in lipid, carbohydrate, and protein metabolism, cellular processes, as well as proteins-transporters was increased. It has been suggested that the wide dissemination of El Tor genovariants is probably due to enhanced pathogenic and adaptive properties and also to the considerable transformation of cell  metabolism.

Objective of the study was to conduct whole-genome sequencing of the vaccine strain Francisella tularensis 15 NIIEG and determine, based on the results, its phylogenetic relationships and the genetic organization features.Materials and methods. Whole-genome sequencing of F. tularensis 15 NIIEG strain was performed on Ion PGM (Ion Torrent, USA) and MinIon (Oxford Nanopore Technologies, UK) platforms. Alignment of readings obtained to the whole-genome of F. tularensis subsp. holarctica LVS (CP009694, USA, 2015) was performed using the software package DNASTAR Lasergene 15.3. Hybrid assembly of reads into contigs was performed by means of Unicycler v. 0.4.4, using data obtained by semiconductor sequencing technology (Ion PGM) and nanopore sequencing (MinIon). Phylogenetic analysis was performed on the basis of single nucleotide polymorphism (SNPs) data located in the core part of F. tularensis genome. Maximum parsimony algorithm was used to construct a dendrogram using the obtained data of common SNP-matrix.Results and discussion. The close relations of F. tularensis 15 NIIEG strain with F. tularensis LVS vaccine strain used in the countries of Western Europe and North America was confirmed. Searching for common single mutations characteristic of F. tularensis 15 vaccine strains of NIIEG and LVS, permitted to find 5 unique SNPs that distinguish them from all other 228 F. tularensis strains used in the comparison. Comparative genomic analysis ofF. tularensis 15 NIIEG vaccine strain and virulent strains revealed in its structure two extensive 526 bp deletions (genes pilA and pilE) and 1480 bp (genes encoding lipoprotein). Similar deletions are also present in the genome of the F. tularensis LVS vaccine strain.

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The aim of this work was to study the composition and functions of intracellular and extracellular proteases of the production Vibrio cholerae strains 569B serovar Inaba and M41 serovar Ogawa using zymographic and proteomic analysis.Materials and methods. Samples of intracellular proteases were obtained from cell lysates by ultrasonication of bacterial cells in a 9 M urea solution. The extracellular protease fraction was precipitated from the culture liquid by adding 50 % trichloroacetic acid to a final concentration of 10 % and incubating on ice. Lyophilized preparations of proteinase K and proteovibrin enzyme complex were used as a control of proteolytic activity. Proteases were detected by substrate gel electrophoresis in 12.5 % polyacrylamide gel impregnated with 0.1 % gelatin, followed by identification of the composition of protein fractions of lysates and exoproteins of both strains using molecular mass spectrometric scanning.Results and discussion. A comparative study of the production strains of V. cholerae 569B serovar Inaba and M41 serovar Ogawa using zymographic and proteomic analysis showed that the greatest enzymatic activity was detected in the fraction of extracellular proteases sample of V. cholerae M41 strain, where five major and four minor zones of gelatin hydrolysis were identified, and high-intensity zones with MW 20–23 and 37–40 kDa were also found in the preparation of proteovibrin isolated from the culture fluid of that strain. As a result of proteomic analysis of the studied strains, 66 enzymes of V. cholerae with different functional activity were reliably identified, among which 15 enzymes had protease activity. The high information content of the complex of modern methods provided for the possibility of identifying qualitative and quantitative differences in the composition of intracellular and extracellular proteases in production strains of V. cholerae, which offers an effective means of screening inter-strain differences in the protease spectrum in production strains.