Roseovarius tolerans gen. nov., sp. nov., a budding bacterium with variable bacteriochlorophyll a production from hypersaline Ekho Lake. (1/358)

Eight Gram-negative, aerobic, pointed and budding bacteria were isolated from various depths of the hypersaline, heliothermal and meromictic Ekho Lake (Vestfold Hills, East Antarctica). The cells contained storage granules and daughter cells could be motile. Bacteriochlorophyll a was sometimes produced, but production was repressed by constant dim light. The strains tolerated a wide range of temperature, pH, concentrations of artificial seawater and NaCl, but had an absolute requirement for sodium ions. Glutamate was metabolized with and without an additional source of combined nitrogen. The dominant fatty acid was C18:1; other characteristic fatty acids were C18:2, C12:0 2-OH, C12:1 3-OH, C16:1, C16:0 and C18:0. The main polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and phosphatidylcholine. The DNA G+C base composition was 62-64 mol%. 16S rRNA gene sequence comparisons showed that the isolates were phylogenetically close to the genera Antarctobacter, 'Marinosulfonomonas', Octadecabacter, Sagittula, Sulfitobacter and Roseobacter. Morphological, physiological and genotypic differences to these previously described and distinct genera support the description of a new genus and a new species, Roseovarius tolerans gen. nov., sp. nov. The type strain is EL-172T (= DSM 11457T).  (+info)

Rubrimonas cliftonensis gen. nov., sp. nov., an aerobic bacteriochlorophyll-containing bacterium isolated from a saline lake. (2/358)

Phenotypic and phylogenetic studies were performed with two strains (OCh 317T and OCh 318; T = type strain) of aerobic chemoheterotrophic bacteriochlorophyll-containing bacteria isolated from water of a saline lake located on the west coast of Australia. Both strains were Gram-negative, short rods and were motile by means of polar flagella. Catalase, oxidase, nitrate reductase, phosphatase and urease were produced. The cells utilized D-glucose, citrate, glycolate, pyruvate and ethanol. Acids were produced from L-arabinose, D-fructose, D-galactose, D-glucose, D-ribose and D-xylose. The strains could grow in media containing 0.5-7.5% NaCl. Bacteriochlorophyll a was synthesized under aerobic conditions. The results of 16S rRNA gene sequence comparisons revealed that strain OCh 317T represented a new lineage in the alpha-3 group of the class Proteobacteria. Strains OCh 317T and OCh 318 were identified as strains of the same species because of their very similar phenotypic characteristics and their previously described high DNA-DNA homology. Therefore, it was concluded that the two strains should be assigned to a new genus and species, for which the name Rubrimonas cliftonensis is proposed. The type strain is OCh 317T (= JCM 10189T).  (+info)

Multiple pathways for ultrafast transduction of light energy in the photosynthetic reaction center of Rhodobacter sphaeroides. (3/358)

A pathway of electron transfer is described that operates in the wild-type reaction center (RC) of the photosynthetic bacterium Rhodobacter sphaeroides. The pathway does not involve the excited state of the special pair dimer of bacteriochlorophylls (P*), but instead is driven by the excited state of the monomeric bacteriochlorophyll (BA*) present in the active branch of pigments along which electron transfer occurs. Pump-probe experiments were performed at 77 K on membrane-bound RCs by using different excitation wavelengths, to investigate the formation of the charge separated state P+HA-. In experiments in which P or BA was selectively excited at 880 nm or 796 nm, respectively, the formation of P+HA- was associated with similar time constants of 1.5 ps and 1. 7 ps. However, the spectral changes associated with the two time constants are very different. Global analysis of the transient spectra shows that a mixture of P+BA- and P* is formed in parallel from BA* on a subpicosecond time scale. In contrast, excitation of the inactive branch monomeric bacteriochlorophyll (BB) and the high exciton component of P (P+) resulted in electron transfer only after relaxation to P*. The multiple pathways for primary electron transfer in the bacterial RC are discussed with regard to the mechanism of charge separation in the RC of photosystem II from higher plants.  (+info)

Kinetics of photoacclimation in cultures of Chromatium vinosum DSM 185 during shifts in light irradiance. (4/358)

Continuous cultures of Chromatium vinosum DSM 185 were shifted from a high to a low irradiance (67 to 4 microE m(-2) s(-1)) and vice versa (4 to 67 microE m(-2) s(-1)). The kinetics of photoacclimation of the cultures were analysed during these transitions until steady state was reached. When irradiance was shifted from 4 to 67 microE m(-2) s(-1), bacteriochlorophyll synthesis halted for 4 h. During this period, pigments were progressively diluted in the newly formed biomass, resulting in a lower specific pigment content. The specific growth rate of the organisms did not change immediately after the shift, but rather underwent a gradual increase during the following 10 h. This transition was accompanied by a transient increase in the levels of glycogen, indicating that CO2 fixation rates increased immediately after the shift, and that unused photosynthate was stored as glycogen. The shift from a high to a low irradiance was characterized by an immediate drop in the specific growth rate to virtually zero, and by comparatively sharp decreases in the specific rates of sulfur and sulfide oxidation and in the specific rate of glycogen accumulation. The specific content of bacteriochlorophyll a increased during the first 10 h. During the same period the specific content of glycogen decreased.  (+info)

Roseateles depolymerans gen. nov., sp. nov., a new bacteriochlorophyll a-containing obligate aerobe belonging to the beta-subclass of the Proteobacteria. (5/358)

Strains 61AT (T = type strain) and 61B2, the first bacteriochlorophyll (BChl) a-containing obligate aerobes to be classified in the beta-subclass of the Proteobacteria, were isolated from river water. The strains were originally isolated as degraders of poly(hexamethylene carbonate) (PHC). The organisms can utilize PHC and some other biodegradable plastics. The strains grow only under aerobic conditions. Good production of BChl a and caroterioid pigments is achieved on PHC agar plates and an equivalent production is observed under oligotrophic conditions on agar medium. Spectrometric results suggest that BChl a is present in light-harvesting complex I and the photochemical reaction centre. The main carotenoids are spirilloxanthin and its precursors. Analysis of the 16S rRNA gene sequence indicated that the phylogenetic positions of the two strains are similar to each other and that their closest relatives are the genera Rubrivivax, ideonella and Leptothrix with similarities of 96.3, 96.2 and 96.1%, respectively. The cells are motile, straight rods and contain poly-beta-hydroxybutyrate granules. Ubiquinone-8 is the predominant quinone. Vitamins are not required for growth. The G + C content of genomic DNA is 66.2-66.3 mol%. Genetic and phenotypic features suggest that the strains represent a new genus in the beta-subclass which is evenly distant from known genera. Consequently, the name Roseateles depolymerans gen. nov., sp. nov. is proposed for the strains; the type strain of Roseateles depolymerans is strain 61AT (= DSM 11813T).  (+info)

Roseivivax halodurans gen. nov., sp. nov. and Roseivivax halotolerans sp. nov., aerobic bacteriochlorophyll-containing bacteria isolated from a saline lake. (6/358)

Phenotypic and phylogenetic studies were performed with two strains (OCh 239T and OCh 210T, T = type strain) of aerobic bacteriochlorophyll-containing bacteria isolated from the charophytes and the epiphytes on the stromatolites, respectively, of a saline lake located on the west coast of Australia. Both strains were chemoheterotrophic, Gram-negative and motile rods with subpolar flagella. Catalase and oxidase were produced. ONPG reaction was positive. Cells utilized D-glucose, acetate, butyrate, citrate, DL-lactate, DL-malate, pyruvate, succinate, L-aspartate and L-glutamate. Acids were produced from D-fructose and D-glucose. Bacteriochlorophyll a was synthesized under aerobic conditions. Strain OCh 239T had nitrate reductase and phosphatase. Acids were produced from L-arabinose, D-galactose, lactose, maltose, D-ribose and sucrose. The strain could grow in 0-20.0% (w/v) NaCl. Strain OCh 210T had urease. Hydrolysis of gelatin was positive. Acids were produced from D-xylose. The strain could grow in 0.5-20.0% (w/v) NaCl. The results of 16S rRNA sequence comparisons revealed that strains OCh 239T and OCh 210T formed a new cluster within the alpha-3 group of the alpha subclass of the class Proteobacteria. The similarity value of the 16S rRNA sequences between strains OCh 239T and OCh 210T was 95.8%. Therefore, it was concluded that these two strains should be placed in a new genus, Roseivivax gen. nov., as the new species Roseivivax halodurans sp. nov. and Roseivivax halotolerans sp. nov. The type species of the genus is Roseivivax halodurans. The type strains of Roseivivax halodurans and Roseivivax halotolerans are OCh 239T (= JCM 10272T) and OCh 210T (= JCM 10271T), respectively.  (+info)

Thiorhodospira sibirica gen. nov., sp. nov., a new alkaliphilic purple sulfur bacterium from a Siberian soda lake. (7/358)

A new purple sulfur bacterium was isolated from microbial films on decaying plant mass in the near-shore area of the soda lake Malyi Kasytui (pH 9.5, 0.2% salinity) located in the steppe of the Chita region of south-east Siberia. Single cells were vibrioid- or spiral-shaped (3-4 microns wide and 7-20 microns long) and motile by means of a polar tuft of flagella. Internal photosynthetic membranes were of the lamellar type. Lamellae almost filled the whole cell, forming strands and coils. Photosynthetic pigments were bacteriochlorophyll a and carotenoids of the spirilloxanthin group. The new bacterium was strictly anaerobic. Under anoxic conditions, hydrogen sulfide and elemental sulfur were used as photosynthetic electron donors. During growth on sulfide, sulfur globules were formed as intermediate oxidation products. They were deposited outside the cytoplasm of the cells, in the peripheral periplasmic space and extracellularly. Thiosulfate was not used. Carbon dioxide, acetate, pyruvate, propionate, succinate, fumarate and malate were utilized as carbon sources. Optimum growth rates were obtained at pH 9.0 and optimum temperature was 30 degrees C. Good growth was observed in a mineral salts medium containing 5 g sodium bicarbonate l-1 without sodium chloride. The new bacterium tolerated up to 60 g sodium chloride l-1 and up to 80 g sodium carbonates l-1. Growth factors were not required. The DNA G + C composition was 56.0-57.4 mol%. Based on physiological, biochemical and genetic characteristics, the newly isolated bacterium is recognized as a new species of a new genus with the proposed name Thiorhodospira sibirica.  (+info)

Bacteriochlorin-protein interactions in native B800-B850, B800 deficient and B800-Bchla(p)-reconstituted complexes from Rhodopseudomonas acidophila, strain 10050. (8/358)

Recently, a method which allows the selective release and removal of the 800 nm absorbing bacteriochlorophyll a (B800) molecules from the LH2 complex of Rhodopseudomonas acidophila strain 10050 has been described [Fraser, N.J. (1999) Ph.D. Thesis, University of Glasgow, UK]. This procedure also allows the reconstitution of empty binding sites with the native pigment Bchla(p), esterified with phytol. We have investigated the bacteriochlorophylla-protein interactions in native, B800 deficient (or B850) and in B8110-bacteriochlorophylla(p)-reconstituted LH2 complexes by resonance Raman spectroscopy. We present the first direct structural evidence which shows that the reconstituted pigments are correctly bound within their binding pockets.  (+info)

• 1
• 2
• 3
• 4
• 5
• 6
• 7
• 8
• 9
• 10