Sporulation of Bacillus subtilis in Binary Cultures with Ultramicrobacteria.

The effect of ultramicrobacterial epibionts of the genera Kaistia (strain NF1), Chryseobacterium (strain NF4), and Stenotrophomonas (strain FM3) on the process of sporulation of Bacillus subtilis ATCC 6633 was studied. The investigated strains of ultramicrobacteria (UMB) were found to inhibit the sporulation process of B. subtilis ATCC 6633 in binary mixed cultures, exhibiting a 3-day delay of the onset of sporulation compared to the control one, an extended period of the prospore maturation, formation of the fraction of immature spores, and development of ultrastructural defects in many endospores. Thus, investigation of binary mixed cultures of B. subtilis and UMB revealed that, apart from suppression of reproduction and lysis of host vegetative cells, inhibition of spore formation and destruction of endospores was yet another feature of intermicrobial parasitism. The UMB parasites of the studied genera are assumed to participate in the regulation of development and reproduction of B. subtilis in natural habitats of this spore-forming bacterium.

[Comparative characteristics of free-living ultramicroscopical bacteria obtained from extremal biotopes].

We isolated 50 strains of free-living ultrasmall bacteria with a cell volume that varies from 0.02 to 1.3 microm3 from a range of extremal natural biotopes, namely permafrost soils, oil slime, soils, lake silt, thermal swamp moss, and the skin integuments of the clawed frog, Xenopus laevis. Of them, 15 isolates, characterized by a cell size of less than 0.1 microm3 and a genome size from 1.5 to 2.4 Mb, were subsumed to ultramicrobacteria belonging to different philogenetic groups (Alphaproteobacteria, Bacteroidetes, Actinobacteria) and genera (Kaistia, Chryseobacterium, Microbacterium, Leucobacter, Leifsonia, and Agrococcus) of the Bacteria domain. They are free-living mesophilic heterotrophic aerobic bacteria. The representatives of Kaistia and Chryseobacterium genera were capable of facultative parasitism on other species of chemo-organotrophic bacteria and cyanobacteria. The ultramicrobacteria differed in their morpholgy, cell ultrastructural organization, and physiological and biochemical features. According to the fine structure of their cell walls, the isolates were subdivided into two groups, namely Gram-positive and Gram-negative forms.

[Study of ectoparasitism of ultramicrobacteria of the genus Kaistia, strains NF1 and NF3 by electron and fluorescence microscopy].

Transmission electron and fluorescence microscopy was used to study the character of the interaction of free-living ultramicrobacterial (UMB) strains NF1 and NF3, affiliated with the genus Kaistia, and seven species of gram-positive and gram-negative heterotrophic bacteria. Strains NF1 and NF3 were found to exhibit parasitic activity against gram-positive Bacillus subtilis and gram-negative Acidovorax delafildii. UMB cells are tightly attached to the envelopes of the victim cells and induce their lysis, thus demonstrating the features of typical ectoparasitism. The selectivity of parasitism of the studied UMB to the victim bacteria has been shown: only two soil microorganisms of the seven test objects, B. subtilis ATCC 6633 and an aerobic gram-negative bacterium A. delafildii 39, were found to be sensitive to UMB attack. Other bacteria (Micrococcus luteus VKM Ac-2230, Staphylococcus aureus 209-P, Pseudomonas putida BS394, Escherichia coli C 600, and Pantoea agglomerans ATCC 27155) were not attacked by UMB. It was established for the first time that free-living UMB may be facultative parasites not only of phototrophic bacteria, as we have previously demonstrated, but of heterotrophic bacteria as well. The UMB under study seem to play an important role in the regulation of the quantity of microorganisms and in the functioning of microbial communities in some natural ecotopes.

[Ultrastructural organization and development cycle of soil ultramicrobacteria belonging to the class Alphaproteobacteria].

Gram-negative chemoorganotrophic soil ultramicrobacteria (UMB), strains NF1 and NF3, have been isolated. In their development cycle, the strains formed small coccoid cells of 400-800 nm and ultrasmall cells of 200-300 nm. Phylogenetically, the strains NF1 and NF3 belong to Alphaproteobacteria and are close to the type strain of the recently described species Kaistia adipata. The ultrastructure of UMB cells has been studied using ultrathin sections and freeze-fracturing. It has been shown that the structure of UMB cell walls is of the gram-negative type; the outer membrane and peptidoglycan layer are well differentiated. The cell surface has numerous protrusions (prosthecae) of conical or spherical shape filled with the contents of the periplasm. The formation of unusual cellular structures (not occurring in known free-living bacteria) is a feature of UMB: these include the following: (a) piles of rod-like subunits, ca. 30 A in diameter and 150-250 angstroms in length: (b) long bunches (up to 300-400 angstroms) comprised of filamentous subunits; and (c) large electron-dense spherical bodies (up to 200-300 angstroms in diameter) localized in the periplasm. A distinctive feature of UMB is their ability to grow as facultative parasites on living cyanobacterial (CB) cells. In this case, three types of interaction between UMB and CB have been revealed: (1) adsorption of UMB cells on the surface of CB cells; (2) penetration of UMB into polysaccharide sheathes; and (3) penetration of UMB into CB eytoplasm. UMB cells have been shown to reproduce by budding, with buds (up to 2-3) located directly on the mother cell, without formation of intennediate hyphae.

[Microbiological analysis of cryopegs from the Varandei Peninsula, Barents Sea].

The paper deals with the microbiological characterization of water-saturated horizons in permafrost soils (cryopegs) found on the Varandei Peninsula (Barents Sea coast), 4-20 m deep. The total quantity of bacteria in the water of cryopegs was 3.5 x 10(8) cells/ml. The population of cultivated aerobic heterotrophic bacteria was 3-4 x 10(7) cells/ml and the number of anaerobic heterotrophic bacteria varied from 10(2) to 10(5) cells/ml depending on cultivation temperature and salinity. Sulfate-reducing bacteria and methanogenic archaea were found as hundreds and tens of cells per ml of water, respectively. A pure culture of a sulfate-reducing strain B15 was isolated from borehole 21 and characterized. Phylogenetic analysis has shown that the new bacterium is a member of the genus Desulfovibrio with Desulfovibrio mexicanus as its closest relative (96.5% similarity). However, the significant phenotypic differences suggest that strain B15 is a new species of sulfate-reducing bacteria.

Link between the early calcium deposition in placenta and nanobacterial-like infection.

The placenta is a vitally important organ in the regulation of embryonic development. That is why extensive calcium deposition [also named as pathological placental calcification (PPC)] could have serious negative consequences for the adequate growth of embryos. The nature and mechanism of PPC development has not been defined as yet. In the present investigation, we have tested the hypothesis that the molecular basis of PPC development consists of nanobacteria-induced calcification in infected female placenta. Electron microscopy findings support this hypothesis. The initial stage of micro-calcification may originate from the external surface of individual nanobacteria-like particles found mainly in placental extracellular matrix, where initial calcium deposition occurs as a needle surface deposition or as an amorphous-like surface precipitate. Further calcific propagation in placenta takes place in the newly formed macro-cavities, which are characterized by low electron density, possibly reflecting its liquid content around calcium deposition. The micro-cavities contain free nanobacterial-like particles, which may relate to atypical Gram-negative bacteria but not to apoptotic bodies by morphological characters and DNA/RNA distribution. We hypothesize that the increased placental calcification might be caused, at least in part, by nanobacterial infection.