Ecophysiological Characteristics of the Mat-forming Bacterium Thioplocain Bottom Sediments of the Frolikha Bay, Northern Baikal

A colorless sulfur bacterium of the genus Thioploca, which forms bacterial mats, was studied in the region of underwater thermal vents (Frolikha Bay, northern Baikal). The organism occurs under microaerobic conditions in top sediment layers, and its biomass can amount to 65 mg of wet weight per 1 kg of silt. Individual filaments of the bacterium penetrate the anaerobic zone to the depth of 19 cm. Thioplocais distributed in a mosaic pattern over the bottom of the bay. Thioplocamats are typically found near vents that discharge low-temperature underground water. In the form of separate filaments, this bacterium is more widely distributed in the top sediment layer, particularly in sediments with a more active sulfate reduction. The bacteria from the deep-water and coastal areas of the bay have different morphology. Cells of Thioplocaare able to accumulate nitrate, and the coefficient of nitrate accumulation in wet bacterial mass in relation to the near-bottom water is 1.3 × 10⁴, suggesting a similarity of metabolism with seawater species. A more lightweight isotopic composition of nitrogen in cell mass as compared to that of representatives of zoobenthos also indicates an active metabolism of nitrogen, apparently, in the process of nitrogen respiration. Comparison of the composition of stable isotopes of carbon in the biomass of representatives of different trophic levels, including Thioploca, found at a depth of 105 m indicates its planktonic origin, whereas, in the deeper bay region, the biomass of Thioplocaincorporates more of the light carbon originating from biogenic methane.     

Sexual transmission of Borrelia garinii by male Ixodes persulcatus ticks (Acari, Ixodidae)

We investigated the transmission of Borrelia garinii and Borrelia afzelii between male and female Ixodes persulcatus ticks. For this purpose the infection rate of partners from tick couples was determined by polymerase chain reaction and reverse line blot. In couples, where the male tick was infected with B. garinii, four out of nine female partners carried B. garinii. In eight couples, male ticks had a dual infection of B. afzelii and B. garinii and three female partners were infected by Borrelia spirochetes. Two female ticks carried B. garinii, and one female tick had a dual infection. No evidence for transmission of B. afzelii from male to female ticks was found among seven couples. In 45 couples where the female tick was infected, not one male tick carried spirochetes. The difference in the B. garinii infection rate between male and female ticks among these couples is highly significant. Our data suggest that transmission of B. garinii from male ticks to female ticks does occur. Sexual transmission of this pathogen may play an important role in the maintenance of B. garinii in I. persulcatus. © Rapid Science Ltd. 1998     

Arthrobacter siderocapsulatus isolated from lake water]

Two microbial strains have been isolated from lake water. The strains oxidize ferrous compounds and manganese. By the structure of microcolonies and the character of deposited oxides of these metals, the strains are identical to the genus Siderocapsa. However, according to their growth cycle and some morpho-physiological characteristics, they were included into the genus Arthrobacter (Corynebacteriaceae). Since these microorganisms differ, by their cultural and morpho-physiological properties, from other species of this genus, they were classed as a new species. Arthrobacter siderocapsulatus nov. sp.     

Comparison of tick-borne microorganism communities in Ixodes spp. of the Ixodes ricinus species complex at distinct geographical regions

Characterizing the tick-borne microorganism communities of Ixodes ricinus (sheep tick) and Ixodes persulcatus (taiga tick) from the I. ricinus species complex in distinct geographical regions of Eastern Europe and European Russia, we demonstrated differences between the two ticks. Taiga ticks were more frequently mono- and co-infected than sheep ticks: 24.4 % (45/184 tested ticks) versus 17.5 % (52/297) and 4.3 % (8/184) versus 3.4 % (10/297), respectively. Ginsberg co-infection index values were significant at the various sites. Diversity of the tick-borne microorganism communities was estimated by the Shannon index, reaching values of 1.71 ± 0.46 and 1.20 ± 0.15 at the sheep-tick and the taiga-tick harbored sites, respectively. Richness of the tick-borne microorganism community in the sheep tick collection sites was about twice the value of the taiga tick collection sites. Future investigations are warranted to further characterize the peculiarities of the tick-borne microorganism communities among the ticks of the Ixodes ricinus complex.     

BiologicalNetworks 2.0 - an integrative view of genome biology data

Background  

A significant problem in the study of mechanisms of an organism's development is the elucidation of interrelated factors which are making an impact on the different levels of the organism, such as genes, biological molecules, cells, and cell systems. Numerous sources of heterogeneous data which exist for these subsystems are still not integrated sufficiently enough to give researchers a straightforward opportunity to analyze them together in the same frame of study. Systematic application of data integration methods is also hampered by a multitude of such factors as the orthogonal nature of the integrated data and naming problems.     

Lithotrophic microorganisms of the oxidative cycles of sulfur and iron

The review deals with sulfur bacteria (the first chemolithotrophs ever studied) and with the acidophilic bacteria of sulfur and iron cycles which were investigated as a result of Winogradsky’s discovery. The diversity of these organisms and the factors and mechanism of its origin are emphasized; their metabolic functions and nutritional regulation are discussed.     

Capacity of Azospirillum thiophilum for lithotrophic growth coupled to oxidation of reduced sulfur compounds

Capacity for lithotrophic growth coupled to oxidation of reduced sulfur compounds was revealed in an Azospirillum strain, A. thiophilum BV-S ^T . Oxygen concentration in the medium was the major factor determining the type of energy metabolism (organotrophic or lithotrophic) in the presence of thiosulfate. Under aerobic conditions, metabolism of A. thiophilum BV-S^T was organoheterotrophic, with thiosulfate oxidation to tetrathionate resulting from the interaction with reactive oxygen species, mostly H₂O₂, which was formed in the electron transport chain in the course of oxidation of organic electron donors. Under microaerobic conditions (2 mg/L O₂ in liquid medium), A. thiophilum BV-S^T carried out lithoheterotrophic (mixotrophic) metabolism; enzymes of the dissimilatory type of sulfur metabolism were responsible for thiosulfate oxidation to tetrathionate and sulfate. Two enzyme systems were found in the cells: thiosulfate dehydrogenase, which catalyzes incomplete oxidation of thiosulfate to tetrathionate and the thiosulfate-oxidizing Sox enzyme complex, which is involved in complete oxidation of thiosulfate to sulfate. The genetic determinant of a Sox complex component in A. thiophilum BV-S^T was revealed. The soxB gene was found, and its expression under microaerobic conditions was observed to increase 32-fold compared to aerobic cultivation.     

Morphophysiological monitoring of winter wheat in spring in the context of global climate warming

Data on morphophysiological monitoring of winter wheat (Triticum aestivum L.) cultivar Mironovskaya 808 grown in Hoagland and Arnon solution in a greenhouse and transferred to natural conditions in March–April 2004 with the mean daily temperature of 0.6 ± 0.7°C within the exposure period of 42 days are presented. Water content, dry weight of plants and their organs, frost hardiness of plants, degree of tissue damage by frost, CO₂ metabolism (photosynthesis and respiration), concentrations of sugars in tissues and proportions between different sugar forms, and activities of soluble and insoluble acid and alkaline phosphatases were monitored. Monitoring was carried out for three experimental variants simulating different microclimatic conditions in spring: after snow melting (experiment I), under ice crust (experiment II), and under snow cover (experiment III). Plants in experiments III and II demonstrated a higher water content in tissues, lower frost hardiness, higher rates of biomass loss, lower concentration of sugars and lower di-to monosaccharide ratio in tissues, and higher total invertase activity, particularly, cell wall-associated acid invertase activity. The dark respiration rates at 0°C did not significantly differ between experimental variants. The photosynthetic capacity at this measurement temperature was maintained in all experimental variants being most pronounced in experiment II with the most intense photoinhibition under natural conditions. Comparison of experiments III and II with experiment I is used to discuss the negative effect of changes in certain microclimatic indices associated with global warming and leading to plant exhaustion and death from frost in spring.     

Molecular heterogeneity of plasma superoxide dismutase.

A method was worked out that helped us to isolate superoxide dismutase (SOD) from human blood plasma. The change of enzyme's activity was shown depending on the period of SOD storage. Changes in activity were observed in storing protein after gel filtration. The activity of purified enzyme was half as much after 24 h storage and remained constant for a long period of time (5 mo). The change of SOD activity was found to be connected with a modification of its structure. The storage of enzyme's solution during 3 1/2 mo is accompanied by the lowering of protein molecular mass from 53,000 Da to 34,000 Da. The inhibitors of proteinases--phenyl-methylsulfonyl fluoride (PMSF) and alpha 2-macroglobulin--showed no protective effects on purified SOD. That's why it was possible to say that the lowering of protein molecular mass didn't connect with a specific proteolysis. An oxidative modification of SOD structure is under discussion now. The modification is most probably caused by oxidative destruction of aminoacid residues that are located outside the protein active centre.