Assessing the Structure of Regulatory Protein Genes in Strains of Genovariants of Vibrio cholerae O1 Biovar El Tor, Isolated in Different Years of the Seventh Cholera Pandemic

The aim of the work was to conduct a comparative analysis of the structure of genes encoding regulatory proteins in strains of Vibrio cholerae O1 biovar El Tor genovariants isolated in cholera endemic and non-endemic territories in different years of the seventh cholera pandemic, and their phylogenetic analysis. Materials and methods. Nucleotide sequences of complete genomes of 75 toxigenic genovariants of V. cholerae O1 El Tor with ctxB1 and ctxB7 alleles listed in NCBI GenBank, ENA, VGARus were used. Bioinformatics analysis was performed using the Blast algorithm (http://blast.ncbi), MEGA X. Phylogenetic analysis was carried out using the REALPHY server. Results and discussion. The structure of 13 loci ( toxT , aphA , aphB , luxO , luxT , gntR , hapR , lysR_vc2383 , lysR_vc1617 , hns , vieA , carR , carS ) was studied. Stable preservation of the aphB and carS genes in the genome of all strains has been established, and toxT , aphA , and luxT have been found in 99 % of them. All genovariants have an altered gntR gene (G565A) encoding a protein that represses gluconate fermentation. The majority of genovariants have an intact hapR gene, unlike the reference strain N16961, which has a thymine deletion at the position 219 in this gene. Some foreign strains include additional mutations in this gene. High variability of the luxO gene has been revealed. Mutations in other regulatory genes have been piling up gradually and stably persisted. During phylogenetic analysis, all the studied strains isolated in different endemic countries and imported to the Russian Federation and neighboring states fell under four clusters in accordance with the structure of regulatory genes. Thus, highly virulent genovariants currently isolated in the endemic territory and imported to the Russian Federation have the genotype hapR (insT219), lysR_vc2383 (C110T), hns (G319A), lysR_vc1617 (A650C), vieA (C235T), carR (G265A).