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Bacterial genomes reflect their adaptation strategies through nucleotide usage trends found in their chromosome composition. Bacteria, unlike eukaryotes contain a wide range of genomic G + C. This wide variability may be viewed as a response to environmental adaptation. Two overarching trends are observed across bacterial genomes, the first, correlates genomic G + C to environmental niches and lifestyle, while the other utilizees intra-genomic G + C incongruence to delineate horizontally transferred material. In this review, we focus on the influence of several properties including biochemical, genetic flows, selection biases, and the biochemical-energetic properties shaping genome composition. Outcomes indicate a trend toward high G + C and larger genomes in free-living organisms, as a result of more complex and varied environments (higher chance for horizontal gene transfer). Conversely, nutrient limiting and nutrient poor environments dictate smaller genomes of low GC in attempts to conserve replication expense. Varied processes including translesion repair mechanisms, phage insertion and cytosine degradation has been shown to introduce higher AT in genomic sequences. We conclude the review with an analysis of current bioinformatics tools seeking to elicit compositional variances and highlight the practical implications when using such techniques. 相似文献
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Arvind Kumar Mungray Khushbu Patel 《International biodeterioration & biodegradation》2011,65(1):23-28
Two full scale up-flow anaerobic sludge blanket (UASB) reactor with activated sludge process based STPs (43 Ml d−1 and 100 Ml d−1 capacities) purely for municipal wastewater having two different aeration systems (surface and diffused) were continuously evaluated for one year. Total coliforms (TC) and fecal coliforms (FC) were measured along with other performance monitoring parameters in raw sewage, UASB effluents, and in final effluents. The concentration of total and fecal coliforms ranged from 9.3 × 106 to 1.2 × 1014 MPN/100 ml and 9.3 × 106 to 2.4 × 1013 MPN/100 ml respectively in raw sewage. At both the plants, it was observed that finally treated effluent still contained significant number of total coliforms (5.71 × 105 and 6.7 × 105) and fecal coliforms (3.67 × 105 and 2.2 × 105) after overall removal of 99.9%, which is still greater than the permissible limit of 1000 MPN/100 ml and needs further treatment. Seasonal variation indicated the effective removal of coliforms in raw sewage was in summer. Fecal coliforms are highly correlated with phosphorous and total coliform concentrations. 相似文献
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Tatiana A. Stromnova Kirill Yu. Monakhov Juan Cmpora Pilar Palma Ernesto Carmona Eleuterio Alvarez 《Inorganica chimica acta》2007,360(15):4111-4116
The first examples of binary palladium(II) derivatives of unsaturated carboxylic acids are reported. It was found that the interaction of Pd3(μ-OAc)6 with the ,β-unsaturated 1-methylcrotonic (tiglic) and crotonic acids leads to the corresponding carboxylates of composition Pd3[μ-O2CC(R′) = CHMe]6, where R′ = Me (1) or H (2). The new compounds have been characterized by elemental analysis, solid and solution IR, 1H and 13C NMR, and ESI mass spectrometry. The crystal structure of 1 has been determined. This molecule displays a central Pd3 cyclic core with Pd–Pd distances of 3.093–3.171 Å. Each Pd–Pd bond is bridged by a pair of carboxylate ligands, one above and the other below the Pd3 plane, providing a square planar coordination for each Pd atom in an approximate D3h overall symmetry arrangement. Solution spectroscopic data show that the bridging η1:η1:μ2 interaction of the carboxylates of 1 and 2 is readily displaced, with a change of the ligand to the terminal (η1) coordination mode. 相似文献
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《BBA》2014,1837(2):264-269
Photosystem II (PSII) is the pigment–protein complex which converts sunlight energy into chemical energy by catalysing the process of light-driven oxidation of water into reducing equivalents in the form of protons and electrons. Three-dimensional structures from x-ray crystallography have been used extensively to model these processes. However, the crystal structures are not necessarily identical to those of the solubilised complexes. Here we compared picosecond fluorescence of solubilised and crystallised PSII core particles isolated from the thermophilic cyanobacterium Thermosynechococcus elongatus. The fluorescence of the crystals is sensitive to the presence of artificial electron acceptors (K3Fe(CN)3) and electron transport inhibitors (DCMU). In PSII with reaction centres in the open state, the picosecond fluorescence of PSII crystals and solubilised PSII is indistinguishable. Additionally we compared picosecond fluorescence of native PSII with PSII in which Ca2 in the oxygen evolving complex (OEC) is biosynthetically replaced by Sr2 +. With the Sr2 + replaced OEC the average fluorescence decay slows down slightly (81 ps to 85 ps), and reaction centres are less readily closed, indicating that both energy transfer/trapping and electron transfer are affected by the replacement. 相似文献
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Nerida G. Wilson Greg W. Rouse Gonzalo Giribet 《Molecular phylogenetics and evolution》2010,54(1):187-193
A consensus on molluscan relationships has yet to be achieved, largely because of conflicting morphological and molecular hypotheses. Monoplacophora show marked seriality of ctenidia, atria, muscles and nephridia and this has been interpreted as plesiomorphic for Mollusca, reflecting a segmented ancestry. More recently this seriality, also partly seen in Polyplacophora, has been seen as a derived condition. Analysis of the first published monoplacophoran DNA sequence from Laevilipilina antarctica Warén & Hain, 1992 [Giribet, G., Okusu, A., Lindgren, A.R., Huff, S., Schrödl, M., Nishiguchi, M.K., 2006. Evidence for a clade composed of molluscs with serially repeated structures: Monoplacophorans are related to chitons. Proc. Natl. Acad. Sci. USA 103, 7723–7728. 10.1073/pnas.0602578103], showed Monoplacophora inside Polyplacophora. These taxa were then grouped under the name Serialia, reflecting the hypothesis that their seriality is a synapomorphy. Subsequent examination revealed that part of the L. antarctica published sequence was the result of contamination with Polyplacophora (Giribet, Supplementary Material S1). We collected and sequenced another monoplacophoran, Laevipilina hyalina McLean, 1979, resulting in the first multi-gene dataset representing all molluscan classes. Our analyses did not show unambiguous support for Serialia. Model-based approaches strongly supported Serialia as a clade, however, parsimony analyses under dynamic and static homology did not resolve the position of Monoplacophora. Although our study provides support for Serialia and none for Conchifera, it appears that further resolution of molluscan relationships will require large increases of data. 相似文献
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Na+- Ca2 + exchanger (NCX) has been proposed to play a role in refilling the sarco/endoplasmic reticulum (SER) Ca2 + pool along with the SER Ca2 + pump (SERCA). Here, SERCA inhibitor thapsigargin was used to determine the effects of SER Ca2 + depletion on NCX–SERCA interactions in smooth muscle cells cultured from pig coronary artery. The cells were Na+-loaded and then placed in either a Na+-containing or in a Na+-substituted solution. Subsequently, the difference in Ca2 + entry between the two groups was examined and defined as the NCX mediated Ca2 + entry. The NCX mediated Ca2 + entry in the smooth muscle cells was monitored using two methods: Ca2 +sensitive fluorescence dye Fluo-4 and radioactive Ca2 +. Ca2 +-entry was greater in the Na+-substituted cells than in the Na+-containing cells when measured by either method. This difference was established to be NCX-mediated as it was sensitive to the NCX inhibitors. Thapsigargin diminished the NCX mediated Ca2 + entry as determined by either method. Immunofluorescence confocal microscopy was used to determine the co-localization of NCX1 and subsarcolemmal SERCA2 in the cells incubated in the Na+-substituted solution with or without thapsigargin. SER Ca2 + depletion with thapsigargin increased the co-localization between NCX1 and the subsarcolemmal SERCA2. Thus, inhibition of SERCA2 leads to blockade of constant Ca2 + entry through NCX1 and also increases proximity between NCX1 and SERCA2. This blockade of Ca2 + entry may protect the cells against Ca2 +-overload during ischemia–reperfusion when SERCA2 is known to be damaged. 相似文献
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Summary. Quercus × warburgii A. Camus, the Cambridge Oak, is a semi‐evergreen tree of hybrid origin, possibly between Q. rugosa Née and Q. robur L., and is only known in cultivation. Mature trees in gardens are extremely rare. Its history and cultivation are discussed. 相似文献
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Summary. The hybrid hazel, Corylus × vilmorinii Rehder is described and illustrated. Its robust habit and showy catkins make it an interesting and worthwhile tree to cultivate. 相似文献
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Summary. Rosa 'Cantabrigiensis' is a hybrid whose history is connected with Cambridge University Botanic Garden where it was raised and first recognised in 1922. Its origin in the experimental work on Rosa by Charles Hurst is discussed, and its likely parentage is given. 相似文献
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Aneuploid cells are frequently observed in human tumors, suggesting that aneuploidy may play an important role in the development of cancer. In this review, I discuss the processes that may give rise to aneuploid cells in normal tissue and in tumors. Aneuploid cells may arise directly from diploid cells through errors in chromosome segregation, as a consequence of incorrect microtubule-kinetochore attachments, or through failure of the spindle checkpoint. A second route to formation of aneuploid cells is through a tetraploid intermediate, where division of tetraploid cells can yield very high rates of chromosome missegregation as a consequence of multipolar spindle formation. Diploid cells may become tetraploid through a variety of mechanisms, including endoreduplication, cell fusion, and cytokinesis failure. Although aneuploid cells may arise from either diploid or tetraploid cells, the fate of the resulting aneuploid cells may be distinct. It is therefore important to understand the different pathways that can give rise to aneuploid cells, and how the varied origins of these cells affect their subsequent ability to survive or proliferate. 相似文献
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《Biochimica et Biophysica Acta (BBA)/General Subjects》2016,1860(2):345-353
BackgroundThe mitochondrial F1FO-ATP synthase has not only the known life function in building most cellular ATP, but also, as recently hinted, an amazing involvement in cell death. Accordingly, the two-faced enzyme complex, which catalyzes both ATP synthesis and ATP hydrolysis, has been involved in the mitochondrial permeability transition, the master player in apoptosis and necrosis. Nitrite, a cellular nitric oxide reservoir, has a recognized role in cardiovascular protection, through still unclear mechanisms.MethodsIn swine heart mitochondria the effect of nitrite on the F1FO-ATPase activity activated by Ca2 +, henceforth defined as Ca-ATPase(s), or by the natural cofactor Mg2 +, was investigated by evaluating ATP hydrolysis under different assay conditions.ResultsCa2 + is far less efficient than the natural cofactor Mg2+ in the ATPase activation. However, when activated by Ca2+ the ATPase activity is especially responsive to nitrite, which acts as uncompetitive inhibitor and up to 2 mM inhibits the Ca2+-activated-ATPase(s), probably by promoting dytirosine formation on the enzyme proteins, leaving the Mg-ATPase(s) unaffected. Most likely these ATPases refer to the same F1FO complex, even if coexistent ATPases may overlap.ConclusionsThe preferential inhibition by nitrite of the Ca-ATPase(s), due to post-translational tyrosine modifications, may prevent the calcium-dependent functionality of the mitochondrial F1FO complex and related events.General significanceIn mitochondria the preferential inhibition of the Ca-ATPase activity/ies by nitrite concentrations which do not affect the coexistent Mg-ATPase(s) may quench the negative events linked to the calcium-dependent functioning mode of the F1FO complex under pathological conditions. 相似文献