Stenotrophomonas maltophilia was discovered as a soil bacterium associated with the rhizosphere. Later, S. maltophilia was found to be a multidrug-resistant hospital-associated pathogen. Lytic bacteriophages are prospective antimicrobials; therefore, there is a need for the isolation and characterization of new Stenotrophomonas phages. The phage StenM_174 was isolated from litter at a poultry farm using a clinical strain of S. maltophilia as the host. StenM_174 reproduced in a wide range of clinical and environmental strains of Stenotrophomonas, mainly S. maltophilia, and it had a podovirus morphotype. The length of the genomic sequence of StenM_174 was 42,956 bp, and it contained 52 putative genes. All genes were unidirectional, and 31 of them encoded proteins with predicted functions, while the remaining 21 were identified as hypothetical ones. Two tail spike proteins of StenM_174 were predicted using AlphaFold2 structural modeling. A comparative analysis of the genome shows that the Stenotrophomonas phage StenM_174, along with the phages Ponderosa, Pepon, Ptah, and TS-10, can be members of the new putative genus Ponderosavirus in the Autographiviridae family. In addition, the analyzed data suggest a new subfamily within this family.

Klebsiella pneumoniae is an important opportunistic pathogen often resistant to antibiotics. Specific phages can be useful in eliminating infection caused by K. pneumoniae. Klebsiella phage vB_KlebPS_265 (KlebP_265) and its host strain were isolated from the sputum of a patient with Klebsiella infection. KlebP_265 was specific mainly to K. pneumoniae-type K2 strains including hypermucoid strains. Most of the hypermucoid KlebP_265-susceptible strains were antibiotic-resistant. This siphophage demonstrated good lytic activity and stability. The KlebP_265 genome was 46,962 bp and contained 88 putative genes; functions were predicted for 37 of them. No genes encoding integrases, toxins, or antibiotic resistance were found in the genome. So, KlebP_265 could potentially be a therapeutic phage. Comparative analysis indicated that KlebP_265 with the most relative Klebsiella phage DP01 formed the putative Dipiunovirus genus. Genome analysis revealed a large monophyletic group of phages related to KlebP_265 and DP01. This group is divided into two monophyletic clusters of phages forming new putative subfamilies Skatevirinae and Roufvirinae. Phylogenetic analysis showed extensive gene exchange between phages from the putative subfamilies. Horizontal transfer even involved conservative genes and led to clear genomic mosaicism, indicating multiple recombination events in the ancestral phages during evolution.

The aim of this research is to study the distribution, species diversity, and genetic variability of rickettsiae in Dermacentor spp. ticks from Western Sib

Stenotrophomonas rhizophila was first discovered in soil; it is associated with the rhizosphere and capable of both protecting roots and stimulating plant growth. Therefore, it has a great potential to be used in biocontrol. The study of S. rhizophila phages is important for a further evaluation of their effect on the fitness and properties of host bacteria. A novel phage StenR_269 and its bacterial host S. rhizophila were isolated from a soil sample in the remediation area of a coal mine. Electron microscopy revealed a large capsid (~Ø80 nm) connected with a short tail, which corresponds to the podovirus morphotype. The length of the genomic sequence of the StenR_269 was 66,322 bp and it contained 103 putative genes; 40 of them encoded proteins with predicted functions, 3 corresponded to tRNAs, and the remaining 60 were identified as hypothetical ones. Comparative analysis indicated that the StenR_269 phage had a similar genome organization to that of the unclassified Xanthomonas phage DES1, despite their low protein similarity. In addition, the signature proteins of StenR_269 and DES1 had low similarity and these proteins clustered far from the corresponding proteins of classified phages. Thus, the StenR_269 genome is orphan and the analyzed data suggest a new family in the class Caudoviricetes.

ЦЕЛЬ ИССЛЕДОВАНИЯ Изучить распространение, видовое разнообразие и генетическую вариабельность риккетсий в клещах Dermacentor spp. на территории Западной Сибири и Северного Казахстана. МАТЕРИАЛ И МЕТОДЫ Образцы от 571 клеща рода Dermacentor (406 Dermacentor reticulatus, 136 Dermacentor nuttalli, 21 Dermacentor marginatus и 8 Dermacentor silvarum) были исследованы на наличие ДНК Rickettsia spp. методом двухраундовой ПЦР. Видовая принадлежность риккетсий была установлена методом видоспецифичной ПЦР и/или секвенированием фрагментов gltA гена. Для ряда образцов Rickettsia raoultii были дополнительно определены нуклеотидные последовательности фрагментов генов ompA (3266 н.п.) и ompB (4852 н.п.). РЕЗУЛЬТАТЫ В исследованных клещах обнаружена ДНК четырех видов риккетсий, а также нового генотипа Rickettsia spp. Ko-97-Dr, не относящегося к известным видам. Все виды клещей наиболее часто были инфицированы R. raoultii; уровень инфицированности варьировал от 47,0 до 86,8%. ДНК Rickettsia sibirica была обнаружена в 16,1—45,7% D. nuttalli на трех участках Республики Алтай. ДНК Rickettsia aeschlimannii, Rickettsia aeschlimannii-like, «Candidatus Rickettsia tarasevichiae» и новый генотип Rickettsia sp. Ko-97-Dr были обнаружены в единичных D. reticulatus и D. marginatus. На основании анализа фрагмента гена gltA было идентифицировано семь сиквенс-вариантов R. raoultii, четыре из которых соответствовали ранее описанным генотипам данного вида. Проведенный анализ образцов R. raoultii по протяженным фрагментам ompA и ompB показал наличие трех генетических групп, соответствующих различным генотипам по гену gltA. ЗАКЛЮЧЕНИЕ В клещах Dermacentor spp. были обнаружены как типичные, так и нетипичные для данных клещей виды риккетсий. Показано существование природных очагов сибирского клещевого тифа на территории Республики Алтай. На основании анализа вариабельных генов поверхностных белков и консервативного гена gltA показано существование трех генетических групп R. raoultii.

Klebsiella pneumoniae is an important opportunistic pathogen often resistant to antibiotics. Specif-ic phages can be useful in eliminating infection caused by K pneumoniae. Klebsiella phage vB_KlebPS_265 (KlebP_265) and its host strain were isolated from the sputum of a patient with Klebsiella infection. KlebP_265 was specific mainly to K. pneumoniae type K2 strains including hypermucoid strains. Most of the hypermucoid KlebP_265-susceptible strains were antibiotic-resistant. This siphophage demonstrated good lytic activity and stability. The KlebP_265 genome was 46,962 bp and contained 88 putative genes; functions were predicted for 37 of them. No genes encoding integrases, toxins, or antibiotic resistance were found in the genome. So, KlebP_265 could potentially be a therapeutic phage. Comparative analysis indicated that KlebP_265 with the most relative Klebsiella phage DP01 formed the putative Dipiunovirus genus. Genome analysis revealed a large monophyletic group of phages related to KlebP_265 and DP01. This group is divided into two monophyletic clusters of phages forming new putative subfamilies Skatevirinae and Roufvirinae. Phylogenetic analysis showed extensive gene exchange between phages from the putative subfamilies. Horizontal transfer even involved conservative genes and led to clear genomic mosaicism, indicating multiple recombination events in the an-cestral phages during evolution.