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31.
Anaerobic ammonium oxidation by anammox bacteria in the Black Sea 总被引:80,自引:0,他引:80
Kuypers MM Sliekers AO Lavik G Schmid M Jørgensen BB Kuenen JG Sinninghe Damsté JS Strous M Jetten MS 《Nature》2003,422(6932):608-611
The availability of fixed inorganic nitrogen (nitrate, nitrite and ammonium) limits primary productivity in many oceanic regions. The conversion of nitrate to N2 by heterotrophic bacteria (denitrification) is believed to be the only important sink for fixed inorganic nitrogen in the ocean. Here we provide evidence for bacteria that anaerobically oxidize ammonium with nitrite to N2 in the world's largest anoxic basin, the Black Sea. Phylogenetic analysis of 16S ribosomal RNA gene sequences shows that these bacteria are related to members of the order Planctomycetales performing the anammox (anaerobic ammonium oxidation) process in ammonium-removing bioreactors. Nutrient profiles, fluorescently labelled RNA probes, 15N tracer experiments and the distribution of specific 'ladderane' membrane lipids indicate that ammonium diffusing upwards from the anoxic deep water is consumed by anammox bacteria below the oxic zone. This is the first time that anammox bacteria have been identified and directly linked to the removal of fixed inorganic nitrogen in the environment. The widespread occurrence of ammonium consumption in suboxic marine settings indicates that anammox might be important in the oceanic nitrogen cycle. 相似文献
32.
G. Röder C. Steinlein M. Schmid K. E. Linsenmair 《Cellular and molecular life sciences : CMLS》1993,49(4):339-341
The karyotype ofD. elongatus was investigated by means of C-banding, silver staining, and mithramycin-and quinacrine fluorescent staining. The diploid chromosome number is 2n=50. C-banding shows pericentromerically localized constitutive heterochromatin in every chromosome. Two of the chromosome pairs carry two telomeric nucleolus organizer regions each. No heteromorphic sex chromosomes were found. 相似文献
33.
Use of the whole-embryo culture technique resulted in experimental evidence that the pathogenesis of exencephaly in mouse embryos after cadmium chloride treatment results from reopening of the cranial neural tube. 相似文献
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35.
Structural polymorphism in chromosome 17 总被引:3,自引:0,他引:3
36.
Lymphocytes of rabbits can be separated from small quantities of heparinized whole blood using a simple density gradient of Ficoll-Ronpacon 1.09. This separation technique yields a pure suspension of viable cells allowing reproducible results from cultures stimulated either with PHA or allogeneic lymphocytes isolated by the same technique. 相似文献
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38.
Dynamin is a GTP-hydrolysing protein that is an essential participant in clathrin-mediated endocytosis by cells. It self-assembles into 'collars' in vitro which also formin vivo at the necks of invaginated coated pits. This self-assembly stimulates dynamin's GTPase activity and it has been proposed that dynamin hydrolyses GTP in order to generate the force needed to sever vesicles from the plasma membrane. A mechanism is now described in which self-assembly of dynamin is coordinated by a domain of dynamin with a GTPase-activating function. Unexpectedly, when dynamin mutants defective in self-assembly-stimulated GTPase activity are overexpressed, receptor-mediated endocytosis is accelerated. The results indicate that dynamin, like other members of the GTPase superfamily, functions as a molecular regulator in receptor-mediated endocytosis, rather than as a force-generating GTPase. 相似文献
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40.
Schmid D Stolzlechner M Sorgner A Bentele C Assinger A Chiba P Moeslinger T 《Cellular and molecular life sciences : CMLS》2012,69(1):129-148
An alternatively spliced form of human sulfonylurea receptor (SUR) 1 mRNA lacking exon 2 (SUR1Δ2) has been identified. The
omission of exon 2 caused a frame shift and an immediate stop codon in exon 3 leading to translation of a 5.6-kDa peptide
that comprises the N-terminal extracellular domain and the first transmembrane helix of SUR1. Based on a weak first splice
acceptor site in the human SUR1 gene (ABCC8), RT-PCR revealed a concurrent expression of SUR1Δ2 and SUR1. The SUR1Δ2/(SUR1 + SUR1Δ2)
mRNA ratio differed between tissues, and was lowest in pancreas (46%), highest in heart (88%) and negatively correlated with
alternative splice factor/splicing factor 2 (ASF/SF2) expression. In COS-7 cells triple transfected with SUR1Δ2/SUR1/Kir6.2,
the SUR1Δ2 peptide co-immunoprecipitated with Kir6.2, thereby displacing two of four SUR1 subunits on the cell surface. The
ATP sensitivity of these hybrid ATP-sensitive potassium channels (KATP) channels was reduced by about sixfold, as shown with single-channel recordings. RINm5f rat insulinoma cells, which genuinely
express SUR1 but not SUR1Δ2, exhibited a strongly increased KATP channel current upon transfection with SUR1Δ2. This led to inhibition of glucose-induced depolarization, calcium flux, insulin
release and glibenclamide action. A non-mutagenic SNP on nucleotide position 333 (Pro69Pro) added another exonic splicing
enhancer sequence detected by ASF/SF2, reduced relative abundance of SUR1Δ2 and slightly protected from non-insulin dependent
diabetes in homozygotic individuals. Thus, SUR1Δ2 represents an endogenous KATP-channel modulator with prodiabetic properties in islet cells. Its predominance in heart may explain why high-affinity sulfonylurea
receptors are not found in human cardiac tissue. 相似文献