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The effect of viruses on the microbial loop, with particular emphasis on bacteria, was investigated over an annual cycle in
2003–2004 in Lake Druzhby and Crooked Lake, two large ultraoligotrophic freshwater lakes in the Vestfold Hills, Eastern Antarctica.
Viral abundance ranged from 0.16 to 1.56 × 109 particles L-1;1 and bacterial abundances ranged from 0.10 to 0.24 × 109 cells L-1;1, with the lowest bacterial abundances noted in the winter months. Virus-to-bacteria ratios (VBR) were consistently low in
both lakes throughout the season, ranging from 1.2 to 8.4. lysogenic bacteria, determined by induction with mitomycin C, were
detected on three sampling occasions out of 10 in both lakes. In Lake Druzhby and Crooked Lake, lysogenic bacteria made up
between 18% and 73% of the total bacteria population during the lysogenic events. Bacterial production ranged from 8.2 to
304.9 × 106 cells L-1;1 day-1;1 and lytic viral production ranged from 47.5 to 718.4 × 106 viruslike particles L-1;1 day-1;1. When only considering primary production, heterotrophic nanoflagellate (HNF) grazing and viral lysis as the major contributors
to the DOC pool (i.e., autochthonous sources), we estimated a high contribution from viruses during the winter months when
>60% of the carbon supplied to the DOC pool originated from viral lysis. In contrast, during the summer <20% originated from
viral lysis. Our study shows that viral process in ultraoligotrophic Antarctic lakes may be of quantitative significance with
respect to carbon flow especially during the dark winter period. 相似文献
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Marjorie R. Lundgren Pascal‐Antoine Christin Emmanuel Gonzalez Escobar Brad S. Ripley Guillaume Besnard Christine M. Long Paul W. Hattersley Roger P. Ellis Richard C. Leegood Colin P. Osborne 《Plant, cell & environment》2016,39(9):1874-1885
C4 photosynthesis is a complex trait resulting from a series of anatomical and biochemical modifications to the ancestral C3 pathway. It is thought to evolve in a stepwise manner, creating intermediates with different combinations of C4‐like components. Determining the adaptive value of these components is key to understanding how C4 photosynthesis can gradually assemble through natural selection. Here, we decompose the photosynthetic phenotypes of numerous individuals of the grass Alloteropsis semialata, the only species known to include both C3 and C4 genotypes. Analyses of δ13C, physiology and leaf anatomy demonstrate for the first time the existence of physiological C3–C4 intermediate individuals in the species. Based on previous phylogenetic analyses, the C3–C4 individuals are not hybrids between the C3 and C4 genotypes analysed, but instead belong to a distinct genetic lineage, and might have given rise to C4 descendants. C3 A. semialata, present in colder climates, likely represents a reversal from a C3–C4 intermediate state, indicating that, unlike C4 photosynthesis, evolution of the C3–C4 phenotype is not irreversible. 相似文献
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Jeong BR Lin Y Joe A Guo M Korneli C Yang H Wang P Yu M Cerny RL Staiger D Alfano JR Xu Y 《The Journal of biological chemistry》2011,286(50):43272-43281
The Pseudomonas syringae type III effector HopU1 is a mono-ADP-ribosyltransferase that is injected into plant cells by the type III protein secretion system. Inside the plant cell it suppresses immunity by modifying RNA-binding proteins including the glycine-rich RNA-binding protein GRP7. The crystal structure of HopU1 at 2.7-Å resolution reveals two unique protruding loops, L1 and L4, not found in other mono-ADP-ribosyltransferases. Site-directed mutagenesis demonstrates that these loops are essential for substrate recognition and enzymatic activity. HopU1 ADP-ribosylates the conserved arginine 49 of GRP7, and this reduces the ability of GRP7 to bind RNA in vitro. In vivo, expression of GRP7 with Arg-49 replaced with lysine does not complement the reduced immune responses of the Arabidopsis thaliana grp7-1 mutant demonstrating the importance of this residue for GRP7 function. These data provide mechanistic details how HopU1 recognizes this novel type of substrate and highlights the role of GRP7 in plant immunity. 相似文献
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Christin Liptow Anne-Marie Tillman Matty Janssen Ola Wallberg Glenn A. Taylor 《The International Journal of Life Cycle Assessment》2013,18(5):1071-1081
Purpose
In order to reduce its environmental impact, the chemical industry no longer produces base chemicals such as ethylene, solely from fossil, but also from biomass-based feedstocks. However, a biomass option suitable for one region might not be as suitable for another region due to, e.g., long transport and the related environmental. Therefore, local biomass alternatives and the environmental impact related to the production of chemicals from these alternatives need to be investigated. This study assesses the environmental impact of producing ethylene from Swedish wood ethanol.Methods
The study was conducted following the methodology of life cycle assessment. The life cycle was assessed using a cradle-to-gate perspective for the production of 50,000 tonnes ethylene/year for the impact categories global warming, acidification (ACP), photochemical ozone creation, and eutrophication (EP).Results and discussion
The production of enzymes used during the life cycle had a significant effect on all investigated impacts. However, reduced consumption of enzyme product, which could possibly be realized considering the rapid development of enzymes, lowered the overall environmental impact of the ethylene. Another approach could be to use alternative hydrolyzing agents. However, little information on their environmental impact is available. An additional key contributor, with regard to ACP, EP, and POCP, was the ethanol production. Therefore, further improvements with regard to the process’ design may have beneficial effects on its environmental impact.Conclusions
The study assessed the environmental impact of wood ethylene and pointed to several directions for improvements, such as improved enzyme production and reduced consumption of enzyme products. Moreover, the analysis showed that further investigations into other process options and increase of ethylene production from biomass are worth continued research. 相似文献89.
Adult neurogenesis in the central olfactory pathway of dendrobranchiate and caridean shrimps: New insights into the evolution of the deutocerebral proliferative system in reptant decapods 下载免费PDF全文
Persistent neurogenesis in the central olfactory pathway characterizes many reptant decapods such as lobsters, crayfish and crabs. In these animals, the deutocerebral proliferative system generates new neurons which integrate into the neuronal network of the first order processing neuropil of the olfactory system, the deutocerebral chemosensory lobes (also called olfactory lobes). However, differences concerning the phenotype and the mechanisms that drive adult neurogenesis were reported in crayfish versus spiny lobsters. While numerous studies have focussed on these mechanisms and regulation of adult neurogenesis, investigations about the phylogenetic distribution are missing. To contribute an evolutionary perspective on adult neurogenesis in decapods, we investigated two representatives of basally diverging lineages, the dendrobranchiate Penaeus vannamei and the caridean Crangon crangon using the thymidine analogue Bromodeoxyuridine (BrdU) as marker for the S phase of cycling cells. Compared to reptant decapods, our results suggest a simpler mechanism of neurogenesis in the adult brain of dendrobranchiate and caridean shrimps. Observed differences in the rate of proliferation and spatial dimensions are suggested to correlate with the complexity of the olfactory system. We assume that a more complex and mitotically more active proliferative system in reptant decapods evolved with the emergence of another processing neuropil, the accessory lobes. © 2018 Wiley Periodicals, Inc. Develop Neurobiol, 2018 相似文献
90.
Isotta Lorenzi Silke Oeljeklaus Abhishek Aich Christin Ronsör Sylvie Callegari Jan Dudek Bettina Warscheid Sven Dennerlein Peter Rehling 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》2018,1865(2):323-333
The three mitochondrial-encoded proteins, COX1, COX2, and COX3, form the core of the cytochrome c oxidase. Upon synthesis, COX2 engages with COX20 in the inner mitochondrial membrane, a scaffold protein that recruits metallochaperones for copper delivery to the CuA-Site of COX2. Here we identified the human protein, TMEM177 as a constituent of the COX20 interaction network. Loss or increase in the amount of TMEM177 affects COX20 abundance leading to reduced or increased COX20 levels respectively. TMEM177 associates with newly synthesized COX2 and SCO2 in a COX20-dependent manner. Our data shows that by unbalancing the amount of TMEM177, newly synthesized COX2 accumulates in a COX20-associated state. We conclude that TMEM177 promotes assembly of COX2 at the level of CuA-site formation. 相似文献