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排序方式: 共有277条查询结果,搜索用时 15 毫秒
81.
Eric D. Becraft Maggie C. Y. Lau Vetter Oliver K. I. Bezuidt Julia M. Brown Jessica M. Labont Kotryna Kauneckaite-Griguole Ruta Salkauskaite Gediminas Alzbutas Joshua D. Sackett Brittany R. Kruger Vitaly Kadnikov Esta van Heerden Duane Moser Nikolai Ravin Tullis Onstott Ramunas Stepanauskas 《The ISME journal》2021,15(10):2830
Sulfate-reducing bacteria Candidatus Desulforudis audaxviator (CDA) were originally discovered in deep fracture fluids accessed via South African gold mines and have since been found in geographically widespread deep subsurface locations. In order to constrain models for subsurface microbial evolution, we compared CDA genomes from Africa, North America and Eurasia using single cell genomics. Unexpectedly, 126 partial single amplified genomes from the three continents, a complete genome from of an isolate from Eurasia, and metagenome-assembled genomes from Africa and Eurasia shared >99.2% average nucleotide identity, low frequency of SNP’s, and near-perfectly conserved prophages and CRISPRs. Our analyses reject sample cross-contamination, recent natural dispersal, and unusually strong purifying selection as likely explanations for these unexpected results. We therefore conclude that the analyzed CDA populations underwent only minimal evolution since their physical separation, potentially as far back as the breakup of Pangea between 165 and 55 Ma ago. High-fidelity DNA replication and repair mechanisms are the most plausible explanation for the highly conserved genome of CDA. CDA presents a stark contrast to the current model organisms in microbial evolutionary studies, which often develop adaptive traits over far shorter periods of time.Subject terms: Environmental microbiology, Molecular evolution, Bacterial genetics 相似文献
82.
J. D. LOZIER N. J. MILLS P. J. PALSB
LL G. K. RODERICK 《Molecular ecology resources》2005,5(3):499-501
Hyalopterus pruni is an invasive aphid pest in California. To study the population biology of this pest both in California and its native Mediterranean region, we have developed 11 di‐ and tri‐nucleotide repeat microsatellite markers. Each locus amplified in individuals representing the full range of geographical regions and host plants where Hyalopterus is found. Polymorphism was high, ranging from six to 22 alleles per locus in the individuals screened. These loci represent the first microsatellites developed for Hyalopterus and they should be of great value in studying the invasion biology and population structure of this insect pest. 相似文献
83.
Hari D Upadhyaya Sangam L Dwivedi Michael Baum Rajeev K Varshney Sripada M Udupa Cholenahalli LL Gowda David Hoisington Sube Singh 《BMC plant biology》2008,8(1):106
Background
Plant genetic resources (PGR) are the basic raw materials for future genetic progress and an insurance against unforeseen threats to agricultural production. An extensive characterization of PGR provides an opportunity to dissect structure, mine allelic variations, and identify diverse accessions for crop improvement. The Generation Challenge Program conceptualized the development of "composite collections" and extraction of "reference sets" from these for more efficient tapping of global crop-related genetic resources. In this study, we report the genetic structure, diversity and allelic richness in a composite collection of chickpea using SSR markers, and formation of a reference set of 300 accessions. 相似文献84.
Pepi M Heipieper HJ Fischer J Ruta M Volterrani M Focardi SE 《Extremophiles : life under extreme conditions》2008,12(3):343-349
Bacillus sp. ORAs2 and Pseudomonas sp. ORAs5, two arsenic-resistant bacterial strains previously isolated from sediments of the Orbetello Lagoon, Italy, were
tested for their adaptation to mixed contaminants on the level of membrane fatty acid composition. The two bacterial strains
were characterized by high levels of arsenic resistance, and Pseudomonas sp. ORAs5 was also shown to be solvent-tolerant. The bacterial strains were exposed to mixtures of two toxic compounds: arsenic
at fixed concentrations and toluene in variable amounts or, alternatively, toluene at constant values along with arsenic added
at variable concentrations. Both strains react to the contaminants by changing the composition of their membrane fatty acids.
Bacillus sp. strain ORAs2 showed a correlation between growth rate decreases and fatty acids degree of saturation increases in both
cases, although pointedly in the presence of 1, 2, and 3 mM of toluene and different additions of arsenic, counteracting membranes
fluidity induced by toxic compounds. In Pseudomonas sp. ORAs5, adaptive changes in membrane composition was observed both in terms of increases in the degree of saturation and
in the trans/cis ratio of unsaturated fatty acids in the presence of varying toluene and constant arsenic concentrations, whereas only minor
changes occurred with increasing arsenic and constant toluene concentrations. Thus, on the level of membrane composition,
Bacillus sp. ORAs2 showed a higher potential for adaptation to the presence of mixed pollutants, suggesting its probable suitability
for bioremediation purposes. 相似文献
85.
The evolutionary radiation of dinosaurs in the Late Triassic and Early Jurassic was a pivotal event in the Earth's history but is poorly understood, as previous studies have focused on vague driving mechanisms and have not untangled different macroevolutionary components (origination, diversity, abundance and disparity). We calculate the morphological disparity (morphospace occupation) of dinosaurs throughout the Late Triassic and Early Jurassic and present new measures of taxonomic diversity. Crurotarsan archosaurs, the primary dinosaur 'competitors', were significantly more disparate than dinosaurs throughout the Triassic, but underwent a devastating extinction at the Triassic-Jurassic boundary. However, dinosaur disparity showed only a slight non-significant increase after this event, arguing against the hypothesis of ecological release-driven morphospace expansion in the Early Jurassic. Instead, the main jump in dinosaur disparity occurred between the Carnian and Norian stages of the Triassic. Conversely, dinosaur diversity shows a steady increase over this time, and measures of diversification and faunal abundance indicate that the Early Jurassic was a key episode in dinosaur evolution. Thus, different aspects of the dinosaur radiation (diversity, disparity and abundance) were decoupled, and the overall macroevolutionary pattern of the first 50Myr of dinosaur evolution is more complex than often considered. 相似文献
86.
Vilius Kviesulaitis Aras Puodziukynas Dainius Haroldas Pauza Vytautas Zabiela Tomas Kazakevicius Raimundas Vaitkevicius Evaldas Diržinauskas Vytenis Semaška Antanas Strazdas Ruta Unikaite Kristina Rysevaite Neringa Pauziene Remigijus Zaliunas 《BMC cardiovascular disorders》2017,17(1):292
Background
Ganglionated plexuses (GP) are terminal parts of cardiac autonomous nervous system (ANS). Radiofrequency ablation (RFA) for atrial fibrillation (AF) possibly affects GP. Changes in heart rate variability (HRV) after RFA can reflect ANS modulation.Methods
Epicardial RFA of GP on the left atrium (LA) was performed under the general anesthesia in 15 mature Romanov sheep. HRV was used to assess the alterations in autonomic regulation of the heart. A 24???hour ECG monitoring was performed before the ablation, 2 days after it and at each of the 12 following months. Ablation sites were evaluated histologically.Results
There was an instant change in HRV parameters after the ablation. A standard deviation of all intervals between normal QRS (SDNN), a square root of the mean of the squared differences between successive normal QRS intervals (RMSSD) along with HRV triangular index (TI), low frequency (LF) power and high frequency (HF) power decreased, while LF/HF ratio increased. Both the SDNN, LF power and the HF power changes persisted throughout the 12???month follow???up. Significant decrease in RMSSD persisted only for 3 months, HRV TI for 6 months and increase in LF/HF ratio for 7 months of the follow???up. Afterwards these three parameters were not different from the preprocedural values.Conclusions
Epicardial RFA of GP’s on the ovine left atrium has lasting effect on the main HRV parameters (SDNN, HF power and LF power). The normalization of RMSSD, HRV TI and LF/HF suggests that HRV after epicardial RFA of GPs on the left atrium might restore over time.87.
88.
Conway LL. Powell 《Plant and Soil》1981,62(2):231-239
Summary White clover and onion plants were grown from seed in pots of sandy loam above pads of mycorrhizal inoculum soil at 0.17–1.40
g/pot (equivalent to 250–2000 kg/ha) and harvested on four occasions. In sterilized soil increasing inoculum rates increased
the onset and size of the mycorrhizal growth response of white clover. In unsterilized soil the indigenous mycorrhizal fungi
greatly stimulated growth of both clover and onion. Nevertheless, all mycorrhizal inoculum rates further stimulated shoot
growth in onion (92% increase over all harvests), while only the highest inoculum rate significantly stimulated clover growth
(52% increase). 相似文献
89.
90.
Sonnhammer EL 《Genome biology》2005,6(1):301
A report on the fourth Cold Spring Harbor Laboratory/Wellcome Trust Conference on Genome Informatics, Hinxton, UK, 22-26 September 2004. 相似文献