The buried China-Russia Crude Oil Pipeline (CRCOP) across the permafrost-associated cold ecosystem in northeastern China carries a risk of contamination to the deep active layers and upper permafrost in case of accidental rupture of the embedded pipeline or migration of oil spills. As many soil microbes are capable of degrading petroleum, knowledge about the intrinsic degraders and the microbial dynamics in the deep subsurface could extend our understanding of the application of in-situ bioremediation. In this study, an experiment was conducted to investigate the bacterial communities in response to simulated contamination to deep soil samples by using 454 pyrosequencing amplicons. The result showed that bacterial diversity was reduced after 8-weeks contamination. A shift in bacterial community composition was apparent in crude oil-amended soils with Proteobacteria (esp. α-subdivision) being the dominant phylum, together with Actinobacteria and Firmicutes. The contamination led to enrichment of indigenous bacterial taxa like Novosphingobium, Sphingobium, Caulobacter, Phenylobacterium, Alicylobacillus and Arthrobacter, which are generally capable of degrading polycyclic aromatic hydrocarbons (PAHs). The community shift highlighted the resilience of PAH degraders and their potential for in-situ degradation of crude oil under favorable conditions in the deep soils.

Oil spills from pipeline ruptures are a major source of terrestrial petroleum pollution in cold regions. However, our knowledge of the bacterial response to crude oil contamination in cold regions remains to be further expanded, especially in terms of community shifts and potential development of hydrocarbon degraders. In this study we investigated changes of microbial diversity, population size and keystone taxa in permafrost soils at four different sites along the China-Russia crude oil pipeline prior to and after perturbation with crude oil. We found that crude oil caused a decrease of cell numbers together with a reduction of the species richness and shifts in the dominant phylotypes, while bacterial community diversity was highly site-specific after exposure to crude oil, reflecting different environmental conditions. Keystone taxa that strongly co-occurred were found to form networks based on trophic interactions, that is co-metabolism regarding degradation of hydrocarbons (in contaminated samples) or syntrophic carbon cycling (in uncontaminated samples). With this study we demonstrate that after severe crude oil contamination a rapid establishment of endemic hydrocarbon degrading communities takes place under favorable temperature conditions. Therefore, both endemism and trophic correlations of bacterial degraders need to be considered in order to develop effective cleanup strategies.

No abstract

As the outermost boundary of the cell, the plasma membrane plays an important role in determining the stress resistance of organisms. To test this concept in a cryophyte, we analyzed alterations of several components in plasma membranes isolated from suspension-cultured cells of Chorispora bungeana Fisch. & C.A. Mey in response to treatment at 0 and -4 degrees C for 192 h. When compared with the controls growing at 25 degrees C, both the membrane permeability and fluidity showed recovery after the initial impairment. Linolenic acid and membrane lipid unsaturation increased by about 0.8-fold following cold treatments, although the kinetics of the increase varied with the temperatures examined. During the treatments, the plasma membrane H(+)-ATPase (EC 3.6.1.3) activity increased by 78.06% at 0 degrees C and 100.47% at -4 degrees C. However, the plasma membrane NADH oxidase (EC 1.6.99.3) activity only decreased when exposed to a lower temperature (-4 degrees C), and remained at 63.93% after being treated for 192 h. After the treatments, the physical properties of the plasma membranes of suspension-cultured cells, especially the -4 degrees C treated cells, were similar to those in the wild plants. These findings indicate that the specific mechanism of cold resistance of C. bungeana is tightly linked with the rapid and flexible regulation of membrane lipids and membrane-associated enzymes, which ensure the structural and functional integrity of the plasma membrane that is essential for withstanding low temperature.

A ω-3 fatty acid desaturase gene from Chorispora bungeana confers multi-stress tolerance by the integrated regulation of membrane, [Ca2+]cyt, ROS, and stress-responsive genes in tobacco

We report a systematic angle-resolved photoemission spectroscopy study on Ba(Fe1−xRux)2As2 for a wide range of Ru concentrations (0.15 ≤ x ≤ 0.74). We observed a crossover from twodimension to three-dimension for some of the hole-like Fermi surfaces with Ru substitution and a large reduction in the mass renormalization close to optimal doping. These results suggest that isovalent Ru substitution has remarkable effects on the low-energy electron excitations, which are important for the evolution of superconductivity and antiferromagnetism in this system. PACS numbers: 74.70.Xa, 71.18.+y, 74.25.Jb, Superconductivity in the iron-based materials usually emerges from a magnetic state by several kinds of routes leading to very similar phase diagrams of magnetism and superconductivity. In Ba 1−x K x Fe 2 As 2 [1] and Ba(Fe 1−x Co x ) 2 As 2 [2], the introduction of extra hole or electron carriers shifts the chemical potential so that the sizes of the hole and electron Fermi surface (FS) pockets evolve oppositely [3], which eventually suppresses the nesting between the hole and electron FS pockets that play a role in the formation of spin-density-wave (SDW) with exotic Dirac cone dispersion [4] in the parent compound. While it is generally believed that external pressure also changes the FS topology by modifying the chemical bonds [5], the role of isovalent element substitution is still debated. Various scenarios, for example changes of the FS topology by chemical pressure [6][7][8], the reduction of electron correlations [8,9], magnetic dilution [10], and even the addition of extra hole carriers [11], have been suggested to explain the suppression of the SDW order with isovalent element substitution in the BaFe 2 (As 1−x P x ) 2 and Ba(Fe 1−x Ru x ) 2 As 2 systems. Surprisingly, only little attention has been devoted to answer the reversed but somehow similarly important question: how does superconductivity is suppressed by increasing the substitution further than the optimal concentration?Since single-crystals can be grown for the entire phase diagram, the Ba(Fe 1−x Ru x ) 2 As 2 system is ideal to investigate the suppression of the SDW order, the emergence of superconductivity and its disappearance with isovalent-substitution. We expect that the electronic structure near the Fermi level (E F ) be substantially modified by the Ru substitution. Indeed, the isovalent Ru substitution at the Fe site leads to an anisotropic lattice distortion, resulting in a strong increase of the As-Fe(Ru)-As bond angle and a decrease of the As height from the Fe(Ru) plane [6,12,13]. The Hall coefficient, which is always negative and decreases with decreasing temperature in the parent compound BaFe 2 As 2 , increases with decreasing temperature in the Ru-substituted samples and even changes sign for large Ru concentrations [13]. With its capacity to resolve dispersive electronic states in the vicinity of E F , angleresolved photoemission spectroscopy (ARPES) is a powerful tool to determine which parameters drive the system from a SDW orde...

No abstract

No abstract