The article presents a study of a crystal-bearing strain, similar in morphological characteristics to the species Bacillus thuringiensis; two types of crystals were studied: bipyramidal and cuboid.

Bacillus cereus sensu lato comprises genetically, morphologically, and physiologically similar gram-positive spore-forming bacterial species with high pathogenic potential, such as B. anthracis, B. cereus, and B. thuringiensis. Toxin-producing strains of B. cereus s.I. pose a major threat to human health. The high degree of similarity between these species makes it very difficult to identify them and to take adequate measures to treat the diseases they cause. Previously, we characterized the clinical isolate CCGC 19/16 belonging to B. cereus s.l. that exhibited features of both B. cereus and B. cytotoxicus. In the present work, CCGC 19/16 was identified as B. cytotoxicus using multilocus sequence typing (MLST) and mass spectrometric analysis. It was also shown that, unlike other representatives of the B. cytotoxicus species, strain CCGC 19/16 is not thermotolerant. Unlike B. cereus, strain CCGC 19/16 is sensitive to most antibiotics and shows increased motility. Like B. cereus strain CCGC 19/16 forms β-hemolysis zones in blood agar. In addition, it has been shown that prolonged storage of samples prior to analysis can lead to misidentification of the isolate. Our results indicate that "rapid methods" of analysis using single genes have insufficient resolving power in the identification of B. cereus s.l. species. The combination of MLST analysis with MALDI-TOF MS provides sufficient resolution.

The article presents data on the sporulation process of Brevibacillus laterosporus, which are of interest due to their biological activity. Crystalline and acrystalline strains of Brevibacillus laterosporus have insecticidal properties.

— Bacillus cereus is a spore-forming bacterium found in the environment mainly in soil. Bacillus spores are known to be extremely resistant not only to environmental factors, but also to various sanitation regimes. This leads to spore contamination of toxin-producing strains in hospital and food equipment and, therefore, poses a great threat to human health. Two clinical isolates identified as B. cereus and B. cytotoxicus were used in the present work. It was shown that their calcium ion content was significantly lower than that of the reference strains. According to electron microscopy, one of the SRCC 19/16 isolates has an enlarged exosporium, and the SRCC 1208 isolate has large electron-dense inclusions of an unclear nature during sporulation. We can assume that these contain a biologically active component with a cytotoxic effect and possibly play a role in pathogenesis. Comparative chemical, biochemical, physiological, and ultrastructural analysis of spores of clinical isolates and reference strains of B. cereus was performed. The results we obtained deepen our understanding of the properties of spores that contribute to the increased pathogenicity of B. cereus group species.

The article analyzes and summarizes the literary and own results of studies of the properties of Brevibacillus laterosporus (Bl) as an agent of biocontrol of insects, microorganisms, and other invertebrates. The review provides data on the morphology and characteristics of the biological properties of Bl. New crystal-bearing strains were reported. The structural features of spores and Bl crystals identified by electron microscopy are discussed. Data on crystal formation in different bacilli are analyzed. Bl crystals have mosquitocidal activity. Data on the antimicrobial properties of Bl, including the activity of Bl against drug-resistant bacteria, are presented. The antimicrobial, fungicidal, and cyanolytic activities of Bl strains make it possible to use them as producers of insecticides, antibiotics, and bacteriocins and as environmentally friendly bacterial agents of biocontrol.

Бациллы Brevibacillus laterosporus (Вl) являются перспективным источником бактериальных инсектицидов. Способность к кристаллообразованию у бактерий Bl до недавнего времени не была установлена. Методами сканирующей и просвечивающей электронной микроскопии охарактеризованы бактериальные клетки Brevibacillus laterosporus. Изучено образование в бактериях белковых кристаллов от первых этапов зарождения в клетках и до стадии появления свободных кристаллов. Получены изображения кристаллов с молекулярным разрешением и определены параметры кристаллической решетки. В случае энтомоцидных бацилл в клетках образуются кристаллические белковые токсины, которые приводят к гибели насекомых после поглощения ими бактерий. Таков механизм защиты этих бактериальных клеток. В этом случае кристаллы выполняют защитную функцию живых организмов.

Интерес к спорообразующим бактериям Bacillus cereus связан с их широкой распространенностью и способностью вызывать различные заболевания, главным образом желудочно-кишечного тракта. Споры патогенных микроорганизмов, в том числе и B. cereus, представляют большую проблему для медицины, фармакологии и пищевой промышленности из-за резистентности к различным факторам внешней среды. Свойства спор обусловлены их ультраструктурой. Базисная структура спор консервативна и состоит из экзоспориума, оболочки, внешней мембраны, кортекса, внутренней мембраны и сердцевины [1]. Однако наружные слои спор, включая экзоспориум, различаются у отдельных видов и штаммов, что позволяет сравнивать особенности их компонентов с помощью электронной микроскопии.

В работе представлена информация о бактерии B. laterosporus, способной образовывать белковые кристаллы, токсичные для некоторых насекомых, что делает данные кристаллы безопасным и экологичным средством для борьбы с москитами. Исследована тонкая структура белковых кристаллов, приведены экспериментальные данные о полученных изображениях методом электронной микроскопии.

В окружающей среде бациллы B. cereus адаптированы к сапрофитному образу жизни. При определенных условиях они могут стать патогенами для человека и животных. Интерес к бациллам В. cereus связан с тем, что они являются причиной заболеваний желудочно-кишечного тракта (ЖКТ), а также могут вызывать септицемию, эндокардит, пневмонию, менингит и др. Важным этапом жизненного цикла В. cereus является спорообразование. Споры В. cereus имеют специфические структуры, отсутствующие у вегетативных клеток и отвечающие за такие свойства спор, как термоустойчивость, резистентность к различным повреждающим факторам, адгезию к биотическим и абиотическим поверхностям. Получены данные о тонкой структуре экзоспориума B. cerеus с помощью просвечивающей электронной микроскопии и компьютерного анализа изображений.

Bacillus cereus повсеместно распространенный вид бацилл. Известно, что B. cerеus является причиной различных заболеваний, главным образом связанных с поражением желудочно-кишечного тракта (ЖКТ) с симптомами диареи и рвоты. В. cerеus может быть этиологическим агентом менингита, перикардита, пневмонии, заболевания глаз, сопутствовать раневым инфекциям. Приведены новые данные о структуре выростов бактерий B. cerеus на основании экспериментальных данных, полученных с помощью просвечивающей электронной микроскопии и компьютерного анализа изображений.

Our study confirmed the capacity of S. pyogenes strains to form biofilms on abiotic surfaces. Chains of streptococci surrounded by bluish film were seen under a microscope after alcian blue staining of the preparations grown on slides. On ultrathin sections in transmission electron microscope, the extracellular matrix (indicator of biofilm maturity) became visible after staining with alcian blue. Microscopy of the sections shows structures characteristic of a biofilm in spaces between the cells. Scanning electron microscopy also demonstrates the presence of a biomembrane. Importantly that type 1M strain forming in fact no membranes when cultured on plastic plates (Costar) formed biofilms on the glass. It seems that the conditions for the biofilm formation on the plastic and on the glass differ, due to which the exopolymeric matrices formed on different surfaces vary by biochemical composition.

HELICOBACTER PYLORI BIOFILM IN VITRO AND IN VIVO Zhukhovitsky V. G.1, 2, 3, Smirnova T. A.1, Shevlyagina N. V. 1, Korzheva I. Yu.2, Didenko L. V. 1, Gintsburg A. L.1, 3 1 Gamaleya Federal Research Centre for Microbiology and Immunology of the Ministry of Public Health 2 Botkin Hospital of Moscow Department of Public Health 3 Sechenov the First Moscow Medical University of the Ministry of Public Health

An issue on the cellular forms that ensure survival of pseudomonads is important due to wide occurrence of these bacteria in the environment and their role for clinical microbiology. The present work demonstrates the high survival potential of Pseudomonas aurantiaca and P. аeruginosa in the mass of exopolymers produced by cells. Exopolymer formation occurred only during incubation of the post-stationary phase cultures of P. aurantiaca (at 4°C) and P. aeruginosa (at 4 and 20°C). After storage for 1.5–12 months, the number of colony-forming units in the exopolymer was 30 to 68% of the viable cell titer in stationary-phase cultures. Antibiotic-tolerant persister cells that were revealed in the exopolymer cultures after treatment with ciprofloxacin (2.5–100 μg/mL) were more resistant to the antibiotic than persisters in suspension cultures, with the threshold doses of 25 and 2.5 μg/mL, respectively. The cells embedded in the exopolymer were found to be more resistant to 5-min heating at 60–70°C than the vegetative cells of suspension cultures, which did not survive such heat treatment conditions. Electron microscopic investigation revealed morphological heterogeneity of exopolymer-embedded pseudomonads, including the presence of the cells similar to cystlike dormant forms. The populations developing on solid media inoculated with the exopolymer mass with cells were found to contain 1.5 to 2 orders of magnitude more persisters tolerant to high ciprofloxacin doses (25 μg/mL for P. aurantiaca and 100 μg/mL for P. aeruginosa) than the populations developing after inoculation with second-transfer vegetative cells of the cells of planktonic cultures. The results obtained improve our understanding of pseudomonad survival in the environment.

Using scanning electron microscopy, the ability of reference and freshly isolated Helicobacter pylori strains to form biofilm under cultivation on abiotic surfaces and in natural conditions was studied. It was shown that both types of strains were capable of biofilm formation in vitro, although reference strains synthesized less pronounced exocellular matrix and flagella than freshly isolated strains. Bio-film also was detected in specimens of antral mucosa under duodenal ulcer. Most often Helicobacter pylori biofilms were detected near the mouths of the gastric glands. The structure of matrix surface of such biofilms looked inhomogeneous in different parts of the epithelial layer.

Compaction and biocrystallization of the nucleoid are presently considered as a necessary and important stage in the transformation of the cell ultrastructure during change of microbial cultures strategies from growth to survival. Nucleoid biocrystallization in the stationary phase cells is achieved due to structural regularity of the DNA complexes with the histone-like Dps protein. Our experiments with Escherichia coli mutants, overproducers of the Dps protein, confirmed nucleoid biocrystallization in the late stationary phase cells. Since nucleoid biocrystallization was revealed in E. сoli cells without Dps overproduction at late stages of starvation, it is constitutive in the cycle of development of microbial populations. The present work concentrated on detection of the nucleoid biocrystalline structure in (1) long-starved (21 day in the chemostat mode) bacterial cells (genera Arthrobacter and Pseudomonas), (2) dormant ametabolic (anabiotic) cells of such prokaryotes as archaea and non-spore-forming bacteria, (3) endospores of bacilli, (4) streptomycete exospores, and (5) in the cells surviving in permafrost for (2‒3 Ma). The topics discussed include nucleoid biocrystallization as a necessary stage of maturation of the dormant microbial cells providing for survival and preservation of the species, dynamics of nucleoid biocrystallization during maturation of the dormant cells, and its possible role for the preservation of genetic information in the case of autolysis of most of the cells in a developing culture.