Microbiology

Phage Particles in Ground Arctic Ice Abstract— This is the first report on investigation of bacteriophages in ancient Arctic ground ice of various genesis and geological age. Electron microscopy revealed phage particles in all ice samples. Tailed bacteriophages were the dominant morphotype. A correlation was found between abundances of intact microbial cells and phage particles. Direct microscopic counts revealed the highest phage abundance melted native samples of ice wedge. Dependence of occurrence and abundance of phage particles on genesis of ground ice was observed. The phages, as an integral component of microbial communities, were found to be preserved in extreme low-temperature conditions of ground ancient ice.

Bacterial Adhesion and Biofilm Formation in the Presence of Chitosan and Its Derivatives Abstract— The effect of chitosan and its derivatives on adhesion and biofilm formation by bacteria with diametrically opposite properties of cell surfaces was studied. Treatment of polystyrene surface with chitosan or its quaternized derivatives was shown to decrease its hydrophobicity significantly, resulting with an over fourfold inhibition of M. smegmatis adhesion. On the contrary, E. coli with hydrophilic cell surface showed higher affinity to the polystyrene surface in the presence of chitosan. The possibility of inhibiting formation of M. smegmatis biofilms by chitosan, which increases its antimycobacterial properties after its quaternization, has not been demonstrated previously. At the same time, the increase in the hydrophobicity of quaternized chitosan resulted in its decreased efficiency against E. coli cells with a relatively hydrophilic surface. The succinylated form of chitosan with negatively charged sites in the structure had practically no antibacterial properties due its decreased ability to bind with the target cells.

Phototrophic Communities of the Berikei Highly Mineralized Mesothermal Sulfide Springs (Dagestan, Russia) Abstract— Phototrophic communities forming in the bottom of the Berikei highly mineralized mesothermal sulfide springs (Kayakent region, Dagestan, Russia) were investigated. The Berikei springs are an interesting example of combined effect of such factors as temperature, salinity, pH, and sulfide of occurrence and structure of phototrophic microbial communities. The water was of the sodium chloride type with salinity of 48‒97 g/L, near-neutral brine pH, and sulfide concentration of ~1 mM. The temperature at the stream bottom was as high as 60°C. Elevated temperature and high salinity limited the development of phototrophic communities. Formation of cyanobacterial mats occurred at temperatures below 54°C. Phormidium-like cyanobacteria and unicellular Synechocystis sp. predominated in the mats. The number of cyanobacterial species increased at desalination to 48‒57 g/L with emergence of the species morphologically resembling Spirulina sp., Leptolyngbya sp., and Oscillatoria sp. Among anoxygenic phototrophic bacteria, halophilic purple bacteria Ectothiorhodospira sp., Marichromatium sp., and Rhodovulum sp., green sulfur bacteria Prosthecochloris sp., and unidentified Chloroflexi were present. Oxygenic photosynthesis in the mats was not inhibited by sulfide. Production of cyanobacterial mats was up to 4.7‒53.8 µg/(cm2 h). The contribution of anoxygenic phototrophic bacteria to photosynthetic production varied from 0 to 100%. The composition of this microbial community was compared to those of the phototrophic microbial communities of the mesothermal springs of the Dead Sea coast (Israel), the Washington warm lake (United States), and the Paoha Island hot springs (Mono Lake, United States.

Rhizobacteria Strain from a Hypersaline Environment Promotes Plant Growth of Kengyilia thoroldiana Abstract Kengyilia thoroldiana is a nutritionally rich grass species of the Qinghai-Tibet Plateau. Here, to improve its quality and biomass via biological fertilization, we sought out plant-growth promoting rhizobacteria. Our screening found one Bacillus species capable of nitrogen fixation, indole-3-acetic acid production, and tolerating the extreme saline-alkali soil of Qinghai Province. We determined the strain's growth performance and antagonistic effects with pathogens (Fusarium graminearum, F. acuminatum) and evaluated its impact on K. thoroldiana. The test strain KKLW1 was identified as Bacillusamyloliquefaciens by morphology, adversity culture, and 16S rDNA and gyrB partial sequence analyses. KKLW1 strongly tolerates saline conditions (11% salt, pH 11), and showed stable nitrogen fixation activity and IAA production capacity; its Phl gene, which we amplified, was significant antagonistic to pathogenic pasture fungi. Furthermore, compared with the control, the strain showed clear germination and growth-promoting activity after soaking grass seeds and root-irrigating with the Bacillussuspension, increasing each by 8 and 10–12%, respectively. In sum, the strain KKLW1 has excellent biological properties and stable physiological characteristics in this extreme environment of the Qinghai-Tibet Plateau. We propose KKLW1 for use as a functional strain of microbial fertilizer to increase production and restore vegetation coverage of the Plateau's grassland.

Optimized Fractioning and Structure Analysis of the Reactivating Factor from Luteococcus japonicus subsp. casei Abstract— The chemical structure of the extracellular reactivating factor (RF) from Luteococcus japonicus subsp. casei was determined; this factor promotes survival of a small subpopulation of the producer cells under lethal stress impact. For the isolation and purification of this RF, the previously developed method for RF isolation from Saccharomyces cerevisiae was optimized. A total of 15 fractions were obtained from the culture liquid of Luteococcus casei, two of which (I and IV) exhibited reactivation activity against the cells subjected to a lethal stress impact (UV irradiation). The method included solid-phase extraction of the peptides on a hydrophobic sorbent with the C8 phase and subsequent multistage separation using RP-HPLC. Mass spectral analysis (MALDI-TOF) was used to determine the molecular characteristics of fraction IV. Efficient ionization was not achieved for fraction I. Mass charges for fraction IV were 773.394 and 788.102 Da. Edman automatic sequencing was used to identify these components as peptides: Ala-Pro-Asn-Glu-Asn-Gln-Gly and Ala-Pro-Asn-Glu-Glu-Gln-Gly. No similarity to any known full-size functional peptide molecules in the databases on polypeptide primary structures was revealed. Formation of biologically active peptides by L. casei may be associated with non-template synthesis and probably involves proteolysis of a large protein.

Iron-Reducing Microbial Communities of the Lake Baikal Low-Temperature Bottom Sediments Abstract— Psychroactive enrichment cultures reducing anthraquinone 2,6-disulfonate (AQDS) and soluble complexes of ferric iron at 5–20°C were isolated from the samples of Lake Baikal bottom sediments collected at the depths of 404 to 1396 m. Cultivation resulted in production of up to 6 mM Fe(II), which was over 50% of the initial Fe(III) concentration in the medium, and of 5.5 mM AH2QDS (~30% of the initial quinone concentration). The enrichment culture of iron-reducing bacteria St3 used Fe(III) citrate as the terminal electron acceptor, oxidizing formate from 6.5 to 2.0 g L–1 at 15°C. Phylogenetic analysis showed that the initial samples of the Lake Baikal bottom sediments and the enrichments obtained from these samples contained the taxa of classes Alpha- and Betaproteobacteria, which were closely related to bacteria capable of oxidizing aromatic compounds using inorganic electron acceptors, including ferric iron.

Ability of the Dietzia , Gordonia and Rhodococcus Actinobacteria to Accumulate Nickel Ions Abstract— Accumulation of nickel ions by actinobacterial strains of Dietzia, Gordonia, and Rhodococcus from the Regional Specialized Collection of Alkanotrophic Microorganisms (IEGM; http://www.iegm.ru/iegmcol) was studied. The major physicochemical factors underlying the accumulation of nickel ions are discussed. The strains characterized by high (up to 95%) accumulation of and resistance to increased (up to 10.0 mM) nickel ion concentrations were selected.

Methacrylate-Reducing Activity of Anaerobic Bacteria Anaeromyxobacter dehalogenans and Denitrovibrio acetiphilus Abstract— Periplasmic methacrylate-reducing activity was shown for anaerobic acetate-oxidizing gram-negative bacteria Anaeromyxobacter dehalogenans 2CP-1Т (class Deltaproteobacteria) and Denitrovibrio acetiphilus DSM 12809Т (class Deferribacteres), both possessing homologous genes for methacrylate redox system components. No acrylate reductase activity was revealed in these bacteria. A. dehalogenans and D. acetiphilus were also found to reduce fumarate, exhibiting periplasmic and intracellular fumarate reductase activity, respectively. D. acetiphilus was found to possess nitrate reductase activity of periplasmic and intracellular localization. The possible correspondence between reductase activities and the hypothetical proteins genes in the known genomes of A. dehalogenans and D. acetiphilus are discussed.

Biofilm Formation by Monocultures and Mixed Cultures of Alcaligenes faecalis 2 and Rhodococcus ruber gt 1 Abstract— Biofilm formation by monocultures and mixed cultures of nitrile-hydrolyzing bacteria Alcaligenes faecalis 2 and Rhodococcus ruber gt 1 was studied. Biofilm formation was assessed by staining with Crystal violet, by the energy state of the cells, and by the output of the polymer matrix. A quantitative method for assessment of the output of the polymer matrix by the fluorescence of konA-tetramethylrhodamine was developed. The medium used for obtaining mixed biofilms of Al. faecalis 2 and R. ruber gt 1 contained acetamide and glucose as carbon sources. In mixed biofilms Al. faecalis 2 was shown to act as a primary colonizer, while R. ruber gt 1 was a satellite microorganism. Compared to monoculture biofilms, mixed biofilms exhibited higher output of the polymer matrix and increased biofilm formation by Al. faecalis 2 and R. ruber gt 1 on addition of the culture liquid of the second strain. Daily addition of the toxic substrate acetonitrile to planktonic and biofilm cultures resulted in bacterial adaptation, as was indicated by higher numbers of surviving cells compared to the variants with acetonitrile addition every 10 min, mainly due to nitrile hydratase activity of R. ruber gt 1, which transformed acetonitrile into nontoxic acetamide. Our results show that binary biofilms of amidase-containing Al. faecalis 2 and R. ruber gt 1, a strain with high nitrile hydratase activity, are promising as biocatalysts for acrylic acid production and as the basis for a biofilter for nitrile removal from wastewater.

Characterization of Ultrasmall Chryseobacterium Strains FM1 and FM2 Isolated from Xenopus laevis Skin Abstract— Two strains of ultrasmall gram-negative bacteria (USGNB), FM1 and FM2, were isolated from the skin of the smooth clawed frog Xenopus laevis. The cytological, physiological, biochemical, and genotypic characteristics of the isolates were studied. Based on the sequencing of their 16S rRNA genes and on their phenotypic properties, the isolates were assigned to the genus Chryseobacterium. The cells were extremely small, with cell volumes of ~0.06 and ~0.015 µm3 for developing cultures of strains FM1 and FM2, respectively. Since the USGNB cells were firmly attached to the skin surface and could not be removed by repeated washing with water, these bacteria may be classified as epibionts. Adhesive properties of the fimbria-like appendages revealed in strains FM1 and FM2 by electron microscopy could probably contribute to tight binding of USGNB cells to the skin. Localization of ultrasmall gram-negative bacteria on skin surface of the frogs may indicate their action as a protective bacterial filter; skin surface of Xenopus laevis is thus characterized for the first time as a specific habitat of ultrasmall Chryseobacterium strains. Isolation and characterization of two ultrasmall Chryseobacterium strains, FM1 and FM2, improves our understanding of diversity of the cellular structural and functional characteristics and of the ecological niches of this bacterial genus.

ALEXANDROS SFAKIANAKIS ANAPAFSEOS 5 AGIOS NIKOLAOS CRETE 72100 GREECE +306932607174 +302841026182