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991.
We have investigated the growth of Escherichia coli, a mesophilic bacterium, as a function of pressure (P) and temperature (T). Escherichia coli can grow and divide in a wide range of pressure (1–400 atm) and temperature (23–40°C). For T > 30°C, the doubling time of E. coli increases exponentially with pressure and exhibits a departure from exponential behavior at pressures between 250 and 400 atm for all the temperatures studied in our experiments. The sharp change in doubling time is followed by a sharp change in phenotypic transition of E. coli at high pressures where bacterial cells switch to an elongating cell type. We propose a model that this phenotypic change in bacteria at high pressures is an irreversible stochastic process, whereas the switching probability to elongating cell type increases with increasing pressure. The model fits well the experimental data. We discuss our experimental results in the light of structural and thus functional changes in proteins and membranes. 相似文献
992.
Emrah Celik Mohd.?Hafeez Faridi Vinay Kumar Shashank Deep Vincent?T. Moy Vineet Gupta 《Biophysical journal》2013,105(11):2517-2527
Integrin CD11b/CD18 is a key adhesion receptor that mediates leukocyte migration and immune functions. Leukadherin-1 (LA1) is a small molecule agonist that enhances CD11b/CD18-dependent cell adhesion to its ligand ICAM-1. Here, we used single-molecule force spectroscopy to investigate the biophysical mechanism by which LA1-activated CD11b/CD18 mediates leukocyte adhesion. Between the two distinct populations of CD11b/CD18:ICAM-1 complex that participate in cell adhesion, the cytoskeleton(CSK)-anchored elastic elements and the membrane tethers, we found that LA1 enhanced binding of CD11b/CD18 on K562 cells to ICAM-1 via the formation of long membrane tethers, whereas Mn2+ additionally increased ICAM-1 binding via CSK-anchored bonds. LA1 activated wild-type and LFA1−/− neutrophils also showed longer detachment distances and time from ICAM-1-coated atomic force microscopy tips, but significantly lower detachment force, as compared to the Mn2+-activated cells, confirming that LA1 primarily increased membrane-tether bonds to enhance CD11b/CD18:ICAM-1 binding, whereas Mn2+ induced additional CSK-anchored bond formation. The results suggest that the two types of agonists differentially activate integrins and couple them to the cellular machinery, providing what we feel are new insights into signal mechanotransduction by such agents. 相似文献
993.
994.
Nupur Bhumika Vaidya Naga Radha Srinivas Tanuku Anil Kumar Pinnaka 《Antonie van Leeuwenhoek》2013,103(2):347-355
A novel marine, Gram-negative, rod-shaped bacterium, designated strain N9T, was isolated from a water sample of the sea shore at Visakhapatnam, Andhra Pradesh (India). Strain N9T was found to be positive for oxidase and catalase activities. The fatty acids were found to be dominated by C16:0, C18:1 ω7c and summed in feature 3 (C16:1 ω7c and/or C16:1 ω6c). Strain N9T was determined to contain Q-10 as the major respiratory quinone and phosphatidylethanolamine, phosphatidylglycerol, two aminophospholipids, two phospholipids and four unidentified lipids as polar lipids. The DNA G+C content of the strain N9T was found to be 63 mol%. 16S rRNA gene sequence analysis indicated that Rhodobacter sphaeroides, Rhodobacter johrii, Pseudorhodobacter ferrugineus, Rhodobacter azotoformans, Rhodobacter ovatus and Pseudorhodobacter aquimaris were the nearest phylogenetic neighbours, with pair-wise sequence similarities of 95.43, 95.36, 94.24, 95.31, 95.60 and 94.74 %, respectively. Phylogenetic analysis showed that strain N9T formed a distinct branch within the family Rhodobacteraceae and clustered with the clade comprising species of the genus Pseudorhodobacter, together with species of the genera Roseicitreum, Roseinatronobacter, Roseibaca and Rhodobaca. Species of the genus Pseudorhodobacter are phylogenetically close with a 16S rRNA gene sequence dissimilarity of 5.9–7.3 % (92.7–94.1 % similarity). Based on the above-mentioned phenotypic characteristics and on phylogenetic inference, strain N9T is proposed as a representative of a new genus and a novel species of the family Rhodobacteraceae as Albirhodobacter marinus gen. nov., sp. nov. The type strain of Albirhodobacter marinus is N9 (= MTCC 11277T = JCM 17680T). 相似文献
995.
996.
Kishan?Kumar Chudasama Jonathon Winnay Stefan Johansson Tor Claudi Rainer K?nig Ingfrid Haldorsen Bente Johansson Ju?Rang Woo Dagfinn Aarskog J?rn?V. Sagen C.?Ronald Kahn Anders Molven P?l?Rasmus Nj?lstad 《American journal of human genetics》2013,93(1):150-157
The phosphatidylinositol 3 kinase (PI3K) pathway regulates fundamental cellular processes such as metabolism, proliferation, and survival. A central component in this pathway is the p85α regulatory subunit, encoded by PIK3R1. Using whole-exome sequencing, we identified a heterozygous PIK3R1 mutation (c.1945C>T [p.Arg649Trp]) in two unrelated families affected by partial lipodystrophy, low body mass index, short stature, progeroid face, and Rieger anomaly (SHORT syndrome). This mutation led to impaired interaction between p85α and IRS-1 and reduced AKT-mediated insulin signaling in fibroblasts from affected subjects and in reconstituted Pik3r1-knockout preadipocytes. Normal PI3K activity is critical for adipose differentiation and insulin signaling; the mutated PIK3R1 therefore provides a unique link among lipodystrophy, growth, and insulin signaling. 相似文献
997.
998.
The synthesis of polyunsaturated fatty acids, the most abundant fatty acids in plants, begins with a reaction catalyzed by fatty acid desaturase-2 (FAD2; EC 1.3.1.35), also called as microsomal Δ12 oleate desaturase. The gene (Bjfad2; GenBank accession No. EF639848) coding for this enzyme from Brassica juncea was previously isolated and characterized. However, functional identity of Bjfad2 was not established. Utilizing the known Bjfad2 cDNA sequence, the ORF of Bjfad2 gene was cloned into the pMAL C2X Escherichia coli expression vector and produced recombinant plasmid by insertion of isolated ORF downstream to the maltose-binding protein coding sequence. The pMALC2X-Bjfad2 vector was used to transform the TB1 strain of E. coli. Induced expression of pMAL-BJFAD2 fused product resulted in the synthesis of a polypeptide with an apparent molecular mass of 80 kDa, which was 8 kDa less than calculated mass as determined by SDS-PAGE, since the fused MalE-Bjfad2 gene contains eight additional codons located between the MalE and Bjfad2 gene. In vitro activity assay of oleate desaturase using the corresponding bacterial crude extracts confirmed that the polypeptide was the product of the Bjfad2 gene. The reaction products analysis of the fatty acid methyl esters by gas chromatography showed the presence of a new peak with a similar retention time to linoleic acid, which was absent in the control activity assay without electron donors. Thus, B. juncea gene has been functionally identified since it encodes the enzyme that catalyzed the desaturation of oleate to linoleate. 相似文献
999.
M. J. Ansari A. Al-Ghamdi R. Kumar S. Usmani Y. Al-Attal A. Nuru A. A. Mohamed K. Singh H. S. Dhaliwal 《Biologia Plantarum》2013,57(3):442-448
Diploid wheat Triticum monococcum L. is a model plant for wheat functional genomics. Chlorophyll-deficient mutant (clm1) was identified during manual screening of the ethyl methanesulphonate (EMS)-treated M2 progenies of T. monococcum accession pau14087 in the field. The clm1 mutant, due to significantly decreased chlorophyll content compared with the wild-type (WT), exhibited pale yellow leaves which slowly recovered to green before flowering. The clm1 mutant showed early flowering, reduced number of tillers, trichome length and density, and different shape as compared with the WT. At the same time, clm1 mutant culm had more chlorophyll-containing parenchymatous tissues compared to WT, presumably to absorb more sunlight for photosynthesis. Genetic analysis indicated that the clm1 mutation was monogenic recessive. The clm1 mutant was mapped between Xgwm473 and Xwmc96 SSR markers, with genetic distances of 2.1 and 2.6 cM, respectively, on the 7AmL chromosome. 相似文献
1000.
Pollen grains of M, and C, generation plants of Trichosanthes anguina L. were studied after treatment of seeds with X-rays and colchicine respectively. Pollen sterility increased with increase in X-ray dose and colchicine concentration. The polar axis of X-irradiated populations was shorter than that of controls. But colchicine treatment resulted in larger pollen grains than the controls, although the exine did not increase as much. Ex-perimentally-produced tetraploids had larger pollen grains than diploids and triploids. The triploids were characterised by changes in pore morphology. Of 293 treated plants examined, 11 aberrant plants were isolated in the M, and C, generations. These plants had large and small fertile pollen grains, and also showed treatment effects in external morphology and chromosomal aberration during meiosis. The changes in polar diameter were not associated with variation in chromosomal material. 相似文献