| Abstract [eng] |
The aim of this work was to biochemically and genetically characterize two novel, virulent bacteriophages VinS9 and RaK2 infecting Salmonella and Klebsiella, respectively. Bioinformatic analyses uncovered that the genomic DNA sequences of bacteriophage VinS9 have the biggest homology with Salmonella phage Vi01 (97-99%) and Shigella phage phiSboM-AG3 (70-80%) which belong to the Myoviridae family. The sequences of Vins9 hypothetical ORFs were determined and it was also shown that they share homology with phage’s T4 essential structural (g21, g22, g23) and functional (g41 (helicase), g61 (primase), g44-62 (DNA clamp-loader subunits), g43 (DNA polymerase)) genes. RaK genome sequences were also analyzed, where ~300 kb of the total ~ 350 kb genome contained 362 hypothetical ORFs showing homologies with essential structural and functional genes of other bacteriophages. It was established, that most of the RaK2 ORFs (63%) do not have reliable homology with sequences of other phages, but are found in other organisms, especially in bacteria. 27% ORFs codes proteins, that share homology with proteins of other phages with identity between 18% and 58% (most of them are the most homological with genome sequences of phage T4). The last 10% ORFs of the phage RaK2 had no homologues in national databases tested. DNA methylation experimental analyses unraveled that RaK2 genomic DNA fragments are methylated, while VinS9 genomic DNA fragments were not. The analysis of phages structural virion proteins showed that the size of hypothetical gp23 protein of phage VinS9 and gp23 of phage T4 are more similar than hypothetical gp23 protein of phage RaK2 and gp23 of phage T4. Meanvile T4 and RaK2 have bigger homology with sequences of gp23 than T4 and VinS9. The complementation tests showed that gp41 of phages VinS9 and RaK2 and gp61, gp44-62 of VinS9 do not restore the functions of the same gene products in phage T4 deletion mutants. Results of this work suggest that in the future phages VinS9 and RaK2 should be classified as members of the family Myoviridae and may form a new subgroup within the super family of T4 related bacteriophages. |
