N2-Fixation by chemoautotrophic hydrogen bacteria

The Gram-positive coryneform bacteria strains 14g and 7C were found to be able to grow with N₂ as sole nitrogen source when incubated under microaerobic conditions. Nitrogenase activity in whole cells was assayed by acetylene reduction. High rates of ethylene production (50–120 nmole/hxmg cell protein) were observed in N₂ or glutamate grown cell suspensions shaken in an atmosphere of 2.5% O₂, 10% acetylene and 87.5% argon.     

Last‐century changes of alpine grassland water‐use efficiency: a reconstruction through carbon isotope analysis of a time‐series of Capra ibex horns

The ecophysiological response of an alpine grassland to recent climate change and increasing atmospheric CO₂ concentration was investigated with a new strategy to go back in time: using a time‐series of Capra ibex horns as archives of the alpine grasslands' carbon isotope discrimination (¹³Δ). From the collection of the Natural History Museum of Bern, horns of 24 males from the population of the Augstmatthorn–Brienzer Rothorn mountains, Switzerland, were sampled covering the period from 1938 to 2006. Samples were taken from the beginning of each year‐ring of the horns, representing the beginning of the horn growth period, the spring. The horns' carbon ¹³C content (Δ¹³C) declined together with that of atmospheric CO₂ over the 69‐year period, but ¹³Δ increased slightly (+0.4‰), though significantly (P<0.05), over the observation period. Estimated intercellular CO₂ concentration increased (+56 μmol mol^?1) less than the atmospheric CO₂ concentration (+81 μmol mol^?1), so that intrinsic water‐use efficiency increased by 17.8% during the 69‐year period. However, the atmospheric evaporative demand at the site increased by approximately 0.1 kPa between 1955 and 2006, thus counteracting the improvement of intrinsic water‐use efficiency. As a result, instantaneous water‐use efficiency did not change. The observed changes in intrinsic water‐use efficiency were in the same range as those of trees (as reported by others), indicating that leaf‐level control of water‐use efficiency of grassland and forests followed the same principles. This is the first reconstruction of the water‐use efficiency response of a natural grassland ecosystem to last century CO₂ and climatic changes. The results indicate that the alpine grassland community has responded to climate change by improving the physiological control of carbon gain to water loss, following the increases in atmospheric CO₂ and evaporative demand. But, effective leaf‐level water‐use efficiency has remained unchanged.     

Properties of Stable Hydrogenase from the Purple Sulfur Bacterium Lamprobacter modestohalophilus

Some properties of a hydrogenase from the recently isolated phototrophic sulfur bacterium Lamprobacter modestohalophilus strain Syvash and its resistance to a number of inactivating factors have been investigated. The enzyme consists of two subunits, 64 and 30 kD; pI = 4.5. The optimal pH was 8.5-9.5 for hydrogen uptake and 4.0 for H2 evolution. Hydrogenase preparations were resistant to the effects of O2, CO, and temperature, revealing high stability under storage. A considerable inactivation of the enzyme was observed at temperatures above 80 degrees C; the temperature optimum of methyl viologen reduction by H2 was 85 degrees C. Inhibitory effects of Ni2+, Cd2+, and Mg2+ on the hydrogenase activity were shown to be reversible and competitive with respect to methyl viologen in the hydrogen oxidation reaction.     

Nucleotide variation in the triosephosphate isomerase (Tpi) locus of Drosophila melanogaster and Drosophila simulans

DNA sequence variation in a 1.1-kb region including the coding portion of the Tpi locus was examined in 25 homozygous third-chromosome lines of Drosophila melanogaster, nine lines of Drosophila simulans, and one line of Drosophila yakuba. Our data show that the widespread allozyme polymorphism observed in cosmopolitan D. melanogaster is due to a glutamic acid substitution occurring in a phylogenetically conserved lysine that has been identified as part of the "hinged-lid" active site of the enzyme. This observation suggests that the replacement polymorphism may have important functional consequences. One replacement polymorphism was also observed in D. simulans, although its functional relevance is more difficult to assess, since it affects a site that is not strongly conserved. This amino acid change in D. simulans is associated with a single lineage possessing seven unique silent substitutions, which may be indicative of balancing selection or population subdivision. The absence of fixed amino acid differences between D. melanogaster and D. simulans and only a single difference with D. yakuba suggests that triose phosphate isomerase is under strong functional constraint. Silent variation is slightly higher for D. melanogaster than for D. simulans. Finally, we outline the general lack of evidence for old balanced polymorphisms at allozyme loci in D. melanogaster.      

Relationships in hydrogen metabolism between hydrogenase and nitrogenase in phototrophic bacteria.

Purple bacteria Rhodospirillum rubrum and Thiocapsa roseopersicina form two enzymes, hydrogenase and nitrogenase, which participate in hydrogen metabolism. H2 photoproduction in these bacteria is associated mainly or completely with the action of nitrogenase. The soluble and membrane-bound hydrogenases of T. roseopersicina have similar physicochemical properties (mol. weight, subunit composition, N-terminal amino acids, Fe2+ and S2- content, pl. Eo'). In comparison with other hydrogenases the enzyme from R. rubrum and T. roseopersicina evolve H2 with high rate from reduced cytochrome c3, but not from ferredoxins. H2 production and N2 fixation take place in the presence of NAD(P)H. NADP-reductase, ferredoxin and cytochrome c3 participate in this reaction. Possible relationships between hydrogenase-nitrogenase in the metabolism of molecular hydrogen are discussed.     

Influence of metal ions on hydrogenase from the purple sulfur bacterium Thiocapsa roseopersicina

The effects of some metal ions on the activity and activation of Thiocapsa roseopersicina hydrogenase have been studied. Inhibitory effects of Ni2+ and Cd2+ on the catalytic activity of the enzyme were reversible and competitive with respect to methyl viologen (MV) in the reaction of hydrogen oxidation. The affinity of these metal ions to the enzyme increased significantly with increasing pH, suggesting that their interactions are determined by electrostatic forces. Cu2+ and Hg2+ irreversibly inhibited the hydrogenase activity. A decrease in absorption of hydrogenase at 400 nm in the presence of these metal ions is indicative of the destruction of the FeS cluster in the enzyme.     

异株藤的离体快繁

1植物名称异株藤(Calamus dioicus)。 2材料类别胚。 3培养条件(1)胚芽生长培养基：MS+6-BA 2．0 mg·L一(单位下同)+4％蔗糖;(2)丛芽诱导培养基：MS+6-BA 4．0+IBA 1．0+NAA 1．0+4％蔗糖;(3)生根培养基1／2MS(大量元素减半)+IBA 0．5+NAA 0．5+3％蔗糖。培养基(1)和(2)加0．7％卡拉胶,培养基(3)加0．73％卡拉胶,pH 5．8±0．2。培养温度(28±2)℃,每天光照10 h,光照度为2 000 k。 4生长与分化情况 4.1 萌发果实大量成熟前一个半月采集近成熟果实,去除果肉得干净种子,用75％酒精浸泡30 s,0．1％升汞表面消毒加～30 min,无菌水冲洗4～5次,在超净台上用刀片将发芽孔打开后转接至培养基(1)。种子在培养基(1)上30 d,与田间播种相同,胚根先长出发芽孔,但受6-BA的作用,胚根长至0．5～1．0 cm即不再进一步生长。接种∞d,胚芽长出发芽孔,∞d长至1．5～2．0 cm高,即可切下胚芽转入丛芽诱导培养基(2)。 4.2 丛芽诱导在培养基(2)中,胚芽高生长明显减缓,基部开始横向膨胀生长,约40d分化出丛芽,丛芽诱导率为30％～35％。     

Low potential c-type cytochrome of Thiocapsa roseopersicina

The low potential c-type cytochrome from the phototrophic purple sulphur bacterium Thiocapsa roseopersicina, strain BBS was isolated in electrophoretically homogeneous state. The bulk of the cytochrome (approximately 90%) after disruption of the cells remained in the membrane fraction. The absorption spectrum of the cytochrome was characterized by the maxima at 420, 523 and 552 nm in the reduced state and at 408 nm in the oxidized one. The cytochrome interacted with CO in the reduced state. The molecular weight of the cytochrome is 50 000. The cytochrome contains great amounts of phenylalanine, leucine, valine, aspartic and glutamic acids and can be reduced by dithionite but not by cysteine, sulfide or ascorbate. Besides, the cytochrome can also be reduced by NAD(P)H in the presence of NAD(P)-reductases of T. roseopersicina, when ferredoxin of Spirulina platensis or benzyl viologen are added to the reaction mixture. The cytochrome can act as an electron donor (acceptor) for T. roseopersicina hydrogenase.