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排序方式: 共有123条查询结果,搜索用时 31 毫秒
1.
Total cellular fatty acids for 20 strains of Erwinia amylovora grown on trypticase soy agar (TSA) for 3 days at 27°C, and for 3 strains grown on nutrient agar (NA), King's B (KB), glucoseyeast extract carbonate (GYCA) and TSA for 1, 3 and 6 days were analyzed by gas-liquid chromatography. Forty one percent of total fatty acids were saturated even-carbon straight chains, 6 % were saturated odd-carbon chains, 34 % unsaturated acids, 6 % hydroxy-substituted acids, 1 % branched chains, 7 % cyclic acids, and 4 % unidentified components. Composition was affected by growth medium, physiological age of cells, and chromatograph sensitivity. On TSA and NA saturated odd-carbon and cyclic acids of the 3 strains (combining 1, 3 and 6-day data) were higher than on KB and GYCA. Cyclic acids increased with physiological age on GYCA and KB medium. Even-carbon straight chain and unsaturated fatty acids (major components) constituted a significantly lower percentage of total fatty acids in chromatograms of high sensitivity (30–50 components) than of low instrument sensitivity (15–20 components). 相似文献
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Excess amino acid polymorphism in mitochondrial DNA: contrasts among genes from Drosophila, mice, and humans 总被引:13,自引:3,他引:10
Recent studies of mitochondrial DNA (mtDNA) variation in mammals and
Drosophila have shown an excess of amino acid variation within species
(replacement polymorphism) relative to the number of silent and replacement
differences fixed between species. To examine further this pattern of
nonneutral mtDNA evolution, we present sequence data for the ND3 and ND5
genes from 59 lines of Drosophila melanogaster and 29 lines of D. simulans.
Of interest are the frequency spectra of silent and replacement
polymorphisms, and potential variation among genes and taxa in the
departures from neutral expectations. The Drosophila ND3 and ND5 data show
no significant excess of replacement polymorphism using the
McDonald-Kreitman test. These data are in contrast to significant
departures from neutrality for the ND3 gene in mammals and other genes in
Drosophila mtDNA (cytochrome b and ATPase 6). Pooled across genes, however,
both Drosophila and human mtDNA show very significant excesses of amino
acid polymorphism. Silent polymorphisms at ND5 show a significantly higher
variance in frequency than replacement polymorphisms, and the latter show a
significant skew toward low frequencies (Tajima's D = -1.954). These
patterns are interpreted in light of the nearly neutral theory where mildly
deleterious amino acid haplotypes are observed as ephemeral variants within
species but do not contribute to divergence. The patterns of polymorphism
and divergence at charge-altering amino acid sites are presented for the
Drosophila ND5 gene to examine the evolution of functionally distinct
mutations. Excess charge-altering polymorphism is observed at the carboxyl
terminal and excess charge-altering divergence is detected at the amino
terminal. While the mildly deleterious model fits as a net effect in the
evolution of nonrecombining mitochondrial genomes, these data suggest that
opposing evolutionary pressures may act on different regions of
mitochondrial genes and genomes.
相似文献
4.
Hydroxyl Radicals and a Thylakoid-Bound Endopeptidase are Involved in Light- and Oxygen-Induced Proteolysis in Oat Chloroplasts 总被引:4,自引:0,他引:4
Casano Leonardo M.; Lascano H. Ramiro; Trippi Victorio S. 《Plant & cell physiology》1994,35(2):145-152
The hypothesis that light- and oxygen-induced proteolysis inchloroplasts is mediated by active oxygen species was examined.In order to determine whether or not H2O2 and/or {dot}OH radicalsare involved in these degradative processes we compared thedegradation of proteins in isolated oat chloroplasts exposedto white light at 80 W m-2 with that in chloroplasts incubatedin darkness in the absence or presence of H2O2 or a {dot}OH-generatingsystem composed by ascorbic acid, FeCl3 and H2O2 (Asc-Fe-H2O2).Light enhanced the rate of degradation of at least 18 polypeptides,while proteolysis was almost negligible in darkness in the abscenceof additives. H2O2 had a very small effect. However, Asc-Fe-H2O2-treatedchloroplasts in darkness showed a pattern of protein degradationalmost identical to that observed in the light. A thylakoid-boundendopeptidase (EP), the activity of which increased under photooxidativeenvironmental conditions and treatment with an {dot}OH-generatingsystem, was partially purified and characterized as a serinetypeprotease. Treatments with inhibitors of serine-type proteaseprevented both light- and Asc- Fe-H2O2-induced proteolysis.EP was more active against both soluble and membranous proteinsthat had been pretreated with Asc-Fe-H2O2 than against untreatedproteins. It is proposed that a high dose of light irradiationpromotes proteolysis by increasing the formation of {dot}OH,which may modify proteins such that they become more susceptibleto EP-catalyzed hydrolysis.
1Fisiología Vegetal, Dept. de Biología Vegetal,Universidad de Alcalá de Henares, Present address: 28871Alcalá de Henares (Madrid), España. 相似文献
5.
Giovanni Spinelli Marialuisa Melli Eva Arnold Caterina Casano Fabrizio Gianguzza Mirella Ciaccio 《Journal of molecular biology》1980,139(2):111-122
Sea urchin RNA extracted from early and mesenchyme blastula embryos and oocytes and fractionated on denaturing sucrose density gradients, was hybridized with histone DNA recombinants of Psammechinus miliaris (clone λh22) and of Paracentrotus lividus (clone pPH70). Histone sequences are found in the 9 S and larger than 9 S regions of the formamide/sucrose density gradients. The melting of the RNA-DNA duplexes obtained by hybridization of polysomal and high molecular weight RNA of embryos of P. lividus at the stage of early blastula, suggests a degree of heterogeneity in the high Mr RNA. The high Mr RNA contains at least four of the five histone gene sequences covalently linked. 相似文献
6.
Eva M. del Campo Leonardo M. Casano Eva Barreno 《Molecular phylogenetics and evolution》2013,66(3):857-867
The RPL10A gene encodes the RPL10 protein, required for joining 40S and 60S subunits into a functional 80S ribosome. This highly conserved gene, ubiquitous across all eukaryotic super-groups, is characterized by a variable number of spliceosomal introns, present in most organisms. These properties facilitate the recognition of orthologs among distant taxa and thus comparative studies of sequences as well as the distribution and properties of introns in taxonomically distant groups of eukaryotes. The present study examined the multiple ways in which RPL10A conservation vs. sequence changes in the gene over the course of evolution, including in exons, introns, and the encoded proteins, can be exploited for evolutionary analysis at different taxonomic levels. At least 25 different positions harboring introns within the RPL10A gene were determined in different taxa, including animals, plants, fungi, and alveolates. Generally, intron positions were found to be well conserved even across different kingdoms. However, certain introns seemed to be restricted to specific groups of organisms. Analyses of several properties of introns, including insertion site, phase, and length, along with exon and intron GC content and exon–intron boundaries, suggested biases within different groups of organisms. The use of a standard primer pair to analyze a portion of the intron-containing RPL10A gene in 12 genera of green algae within Chlorophyta is presented as a case study for evolutionary analyses of introns at intermediate and low taxonomic levels. Our study shows that phylogenetic reconstructions at different depths can be achieved using RPL10A nucleotide sequences from both exons and introns as well as the amino acid sequences of the encoded protein. 相似文献
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Sara Santarossa Alexandra R. Sitarik Christine Cole Johnson Jia Li Susan V. Lynch Dennis R. Ownby Alex Ramirez Germaine LM. Yong Andrea E. Cassidy-Bushrow 《Journal of Exercise Nutrition & Biochemistry》2021,25(4):24
[Purpose] To determine whether physical activity (PA), primarily the recommended 60 minutes of moderate-to-vigorous PA, is associated with gut bacterial microbiota in 10-year-old children.[Methods] The Block Physical Activity Screener, which provides minutes/day PA variables, was used to determine whether the child met the PA recommendations. 16S rRNA sequencing was performed on stool samples from the children to profile the composition of their gut bacterial microbiota. Differences in alpha diversity metrics (richness, Pielou’s evenness, and Faith’s phylogenetic diversity) by PA were determined using linear regression, whereas beta diversity (unweighted and weighted UniFrac) relationships were assessed using PERMANOVA. Taxon relative abundance differentials were determined using DESeq2.[Results] The analytic sample included 321 children with both PA and 16S rRNA sequencing data (mean age [SD] =10.2 [0.8] years; 54.2% male; 62.9% African American), where 189 (58.9%) met the PA recommendations. After adjusting for covariates, meeting the PA recommendations as well as minutes/day PA variables were not significantly associated with gut richness, evenness, or diversity (p ≥ 0.19). However, meeting the PA recommendations (weighted UniFrac R2 = 0.014, p = 0.001) was significantly associated with distinct gut bacterial composition. These compositional differences were partly characterized by increased abundance of Megamonas and Anaerovorax as well as specific Christensenellaceae_R-7_group taxa in children with higher PA.[Conclusion] Children who met the recommendations of PA had altered gut microbiota compositions. Whether this translates to a reduced risk of obesity or associated metabolic diseases is still unclear. 相似文献