Цель работы. Анализ возможности длительного сохранения штаммов Y. pestis в ассоциации с амебами Acanthamoeba sp. Материалы и методы. Исследовано взаимодействие амеб Acanthamoeba sp., выделенных из почв нор грызунов в Прикаспийском песчаном, Волго-Уральском степном и Прикаспийском Северо-Западном степном природных очагах чумы, с 4 штаммами Y. pestis основного подвида, 1 штаммом кавказского и 1 штаммом алтайского подвида. Результаты и обсуждение. Установлено, что штаммы основного подвида сохраняются в клетках амеб при температуре 26 °С и влажности 20 % (моделирование засушливых периодов в природных очагах чумы) в течение двух-четырех месяцев проведения эксперимента и в 10-20 раз дольше, чем в чистой культуре. Два штамма неосновных подвидов не показали увеличения длительности выживания в ассоциации с акантамебами, что может быть связано с их пониженной резистентностью к фагоцитозу амебами этого рода. Методами флуоресцентной и электронной трансмиссионной микроскопии установлено, что клетки возбудителя чумы сохраняются в клетках амеб в индивидуальных вакуолях, окруженных эндоплазматическим ретикулумом. Полученные данные могут свидетельствовать о возможном участии амеб Acanthamoeba sp. в сохранении Y. pestis в почвенных биоценозах природных очагов чумы.
In non-pigmented and plasmid-deprived mutants-isogenic variants of highly virulent Yersinia pestis 231 strain-studied is the mechanism of biofilm formation on biotic surfaces, both in vitro (on the laboratory model of nematode Caenorhabdiitis elegans) and in vivo (inside the alimentary tract of Nosopsyllus laeviceps flea). It is determined that spontaneous loss of ability to form biofilms and generate pigmented colonies in the mutants is probably caused not only by the deletion of the whole chromosome pigmentation fragment, but also by a point(single base) mutation in structural hms operon. It is demonstrated that the absence of pCad, pFra or pPst plasmids does not have an impact on the ability of plasmid-deprived mutants to form biofilm on the cuticle of nematode C. elegans.
An analysis of a 5.4 kb cryptic plasmid detected in the course of whole genome sequencing of the Yersinia pestis medieval biovar strain isolated in the Russian Central Caucasian high mountain plague focus was performed. The identification of the nucleotide sequence of this cryptic plasmid and its structural and functional analysis revealed that it contained eight open reading frames, among which the following genes were identified: the rep gene of a replication protein, the virB6 gene of a type IV secretion system inner mem brane protein, the virB5 gene of the type IV secretion system minor pilin, and a number of genes probably associated with secretion and transport. A general analysis of the pCKF plasmid DNA showed that the ade nine content was 28.34%, the cytosine content was 20.5%, the guanine content was 17.87%, and that of thymine was 33.28%, while the total G+C content appeared to be 38.38%. The G+C content of the chromo some of the Y. pestis strain C 627 is 47.6%, which indicates that the pCKF plasmid was obtained from a microorganism phylogenetically distant from the Yersinia bacteria and any other bacteria from the Entero bacteriaceae family. A comparison of the amino acid sequences of hypothetical proteins encoded by pCKF plasmid with analogous proteins encoded by other bacteria was carried out. The possible contribution of the pCKF plasmid to the maintenance of the most ancient known phylogenetic line of Y. pestis medieval biovar, 2.MED0, was discussed.
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