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631.
P. H. Janssen Alexandra Schuhmann F. Bak Werner Liesack 《Archives of microbiology》1996,166(3):184-192
A new strictly anaerobic, gram-negative bacterium was isolated from the sediment of a freshwater lake after enrichment with
thiosulfate as the energy source. The strain, named Bra2 (DSM 7269), is able to grow by disproportionation of thiosulfate
or sulfite to sulfate plus sulfide. Elemental sulfur is also disproportionated to sulfate and sulfide, but this only supports
growth if free sulfide is chemically removed from the culture, e.g., by precipitation with amorphous ferric hydroxide. Growth
is also possible by coupling the reduction of sulfate to sulfide with the oxidation of ethanol, propanol, or butanol to the
corresponding fatty acid. The cells are rod-shaped, motile, and have genomic DNA with a mol% G+C content of 50.7. Cytochromes
are present, but desulfoviridin is not. The new strain was shown to be related to, but distinct from members of the genus
Desulfobulbus on the basis of physiological characteristics and by comparative sequence analysis of its 16S rDNA. Strain Bra2 is described
as the type strain of a new taxon, Desulfocapsa thiozymogenes gen. nov., sp. nov.
Received: 29 January 1996 / Accepted: 31 May 1996 相似文献
632.
Jeh Haur Wong Martina Klejchov Stephen A Snipes Punita Nagpal Gwangbae Bak Bryan Wang Sonja Dunlap Mee Yeon Park Emma N Kunkel Brendan Trinidad Jason W Reed Michael R Blatt William M Gray 《Plant physiology》2021,185(1):256
Activation of plasma membrane (PM) H+-ATPase activity is crucial in guard cells to promote light-stimulated stomatal opening, and in growing organs to promote cell expansion. In growing organs, SMALL AUXIN UP RNA (SAUR) proteins inhibit the PP2C.D2, PP2C.D5, and PP2C.D6 (PP2C.D2/5/6) phosphatases, thereby preventing dephosphorylation of the penultimate phosphothreonine of PM H+-ATPases and trapping them in the activated state to promote cell expansion. To elucidate whether SAUR–PP2C.D regulatory modules also affect reversible cell expansion, we examined stomatal apertures and conductances of Arabidopsis thaliana plants with altered SAUR or PP2C.D activity. Here, we report that the pp2c.d2/5/6 triple knockout mutant plants and plant lines overexpressing SAUR fusion proteins exhibit enhanced stomatal apertures and conductances. Reciprocally, saur56 saur60 double mutants, lacking two SAUR genes normally expressed in guard cells, displayed reduced apertures and conductances, as did plants overexpressing PP2C.D5. Although altered PM H+-ATPase activity contributes to these stomatal phenotypes, voltage clamp analysis showed significant changes also in K+ channel gating in lines with altered SAUR and PP2C.D function. Together, our findings demonstrate that SAUR and PP2C.D proteins act antagonistically to facilitate stomatal movements through a concerted targeting of both ATP-dependent H+ pumping and channel-mediated K+ transport.SMALL AUXIN UP RNA (SAUR) proteins and PP2C.D phosphatases antagonistically regulate stomatal aperture in Arabidopsis by modulating the activities of plasma membrane H+-ATPases and K+ channels. 相似文献
633.
Eighty-seven different enterobacteria and pseudomonas strains were examined for the presence of extrachromosomal deoxyribonucleic acid (DNA). Thirty-four strains contained closed circular DNA by the ethidium bromide CsCl density technique. Extrachromosomal DNA was most frequent in Escherichia and Klebsiella strains. The extrachromosomal DNA was isolated and characterized by analytical ultracentrifugation and electron microscopy. All the extrachromosomal DNA-containing bacteria contained circular DNA molecules of small size (0.5-4 mum). Most of these bacteria also contained larger circles (20-40 mum). The number of different size classes of circular DNA in each strain varied from one to five. The buoyant density of the extrachromosomal DNA ranged from 1.692 to 1.721 g/cm(3). Many bacteria contained extrachromosomal DNA of more than one density. 相似文献
634.
R. P. M. Bak 《Coral reefs (Online)》1994,13(2):99-103
Two aspects of erosion by sea urchins (Echinoidea) in coral reef habitats are: the direct passage of reef framework material through the gut and the indirect effects through the weakening of the reef structure. Urchin bioerosion can equal or exceed reef carbonate production. The impact of urchins on reefs depends on three variables: species type, test size and population density. Large differences in bioerosion by urchins of the same test size occur between different species. Size differences between species in a sea urchin community, as well as size differences within a species along a reef, can be significant. Bioerosion per urchin increases enormously with size. Changes in population density, through time and space, result in significant changes in bioerosion. It is demonstrated how the interaction of these variables determines in-situ sea urchin bioerosion. 相似文献
635.
Frederic Torossian Aurelie Bisson Jean-Pierre Vannier Olivier Boyer Marek Lamacz 《Cellular & molecular biology letters》2010,15(4):600-610
Transient receptor potential canonical (TRPC) channels are key players in calcium homeostasis and various regulatory processes
in cell biology. Little is currently known about the TRPC subfamily members in mesenchymal stem cells (MSC), where they could
play a role in cell proliferation. We report on the presence of TRPC1, 2, 4 and 6 mRNAs in MSC. Western blot and immunofluorescence
staining indicate a membrane and intracellular distribution of TRPC1. Furthermore, the decrease in the level of TRPC1 protein
caused by RNA interference is accompanied by the downregulation of cell proliferation. These results indicate that MSC express
TRPC1, 2, 4 and 6 mRNA and that TRPC1 may play a role in stem cell proliferation. 相似文献
636.
637.
Nicholas A. Roy Ji Hyun Bak Athena Akrami Carlos D. Brody Jonathan W. Pillow 《Neuron》2021,109(4):597-610.e6
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638.
Kook Han Kwang-sun Kim Geunu Bak Hongmarn Park Younghoon Lee 《Nucleic acids research》2010,38(17):5851-5866
Five Sib antitoxin RNAs, members of a family of cis-encoded small regulatory RNAs (sRNAs) in Escherichia coli, repress their target mRNAs, which encode Ibs toxins. This target repression occurs only between cognate sRNA–mRNA pairs with an exception of ibsA. We performed co-transformation assays to assess the ability of SibC derivatives to repress ibsC expression, thereby revealing the regions of SibC that are essential for ibsC mRNA recognition. SibC has two target recognition domains, TRD1 and TRD2, which function independently. The target site for TRD1 is located within the ORF of ibsC, whereas the target site for TRD2 is located in the translational initiation region. The TRD1 sequence is sufficient to repress ibsC expression. In contrast, TRD2 requires a specific structure in addition to the recognition sequence. An in vitro structural probing analysis showed that the initial interactions at these two recognition sites allowed base-pairing to progress into the flanking sequences. Displacement of the TRD1 and TRD2 domains of SibC by the corresponding domains of SibD changed the target specificity of SibC from ibsC to ibsD, suggesting that these two elements modulate the cognate target recognition of each Sib RNA by discriminating among non-cognate ibs mRNAs. 相似文献
639.
Aurelie Lachish-Zalait Corine K. Lau Boris Fichtman Ella Zimmerman Amnon Harel Michelle R. Gaylord Douglass J. Forbes Michael Elbaum 《Traffic (Copenhagen, Denmark)》2009,10(10):1414-1428
Delivery of DNA to the cell nucleus is an essential step in many types of viral infection, transfection, gene transfer by the plant pathogen Agrobacterium tumefaciens and in strategies for gene therapy. Thus, the mechanism by which DNA crosses the nuclear pore complex (NPC) is of great interest. Using nuclei reconstituted in vitro in Xenopus egg extracts, we previously studied DNA passage through the nuclear pores using a single-molecule approach based on optical tweezers. Fluorescently labeled DNA molecules were also seen to accumulate within nuclei. Here we find that this import of DNA relies on a soluble protein receptor of the importin family. To identify this receptor, we used different pathway-specific cargoes in competition studies as well as pathway-specific dominant negative inhibitors derived from the nucleoporin Nup153. We found that inhibition of the receptor transportin suppresses DNA import. In contrast, inhibition of importin β has little effect on the nuclear accumulation of DNA. The dependence on transportin was fully confirmed in assays using permeabilized HeLa cells and a mammalian cell extract. We conclude that the nuclear import of DNA observed in these different vertebrate systems is largely mediated by the receptor transportin. We further report that histones, a known cargo of transportin, can act as an adaptor for the binding of transportin to DNA. 相似文献