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排序方式: 共有116条查询结果,搜索用时 15 毫秒
61.
Mathieu Groussin Bastien Boussau Sandrine Charles Samuel Blanquart Manolo Gouy 《Biology letters》2013,9(5)
Several lines of evidence such as the basal location of thermophilic lineages in large-scale phylogenetic trees and the ancestral sequence reconstruction of single enzymes or large protein concatenations support the conclusion that the ancestors of the bacterial and archaeal domains were thermophilic organisms which were adapted to hot environments during the early stages of the Earth. A parsimonious reasoning would therefore suggest that the last universal common ancestor (LUCA) was also thermophilic. Various authors have used branch-wise non-homogeneous evolutionary models that better capture the variation of molecular compositions among lineages to accurately reconstruct the ancestral G + C contents of ribosomal RNAs and the ancestral amino acid composition of highly conserved proteins. They confirmed the thermophilic nature of the ancestors of Bacteria and Archaea but concluded that LUCA, their last common ancestor, was a mesophilic organism having a moderate optimal growth temperature. In this letter, we investigate the unknown nature of the phylogenetic signal that informs ancestral sequence reconstruction to support this non-parsimonious scenario. We find that rate variation across sites of molecular sequences provides information at different time scales by recording the oldest adaptation to temperature in slow-evolving regions and subsequent adaptations in fast-evolving ones. 相似文献
62.
B. Montuelle U. Dorigo A. Bérard B. Volat A. Bouchez A. Tlili V. Gouy S. Pesce 《Hydrobiologia》2010,657(1):123-141
Developing new biological indicators for monitoring toxic substances is a major environmental challenge. Intensive agricultural
areas are generally pesticide-dependent and generate water pollution due to transfer of pesticide residues through spray-drift,
run-off and leaching. The ecological effects of these pollutants in aquatic ecosystems are broad-ranging owing to the variety
of substances present (herbicides, fungicides, insecticides, etc.). Biofilms (or periphyton) are considered to be early warning
systems for contamination detection and their ability to reveal effects of pollutants led researchers to propose a variety
of methods to detect and assess the impact of pesticides. The present article sought to provide new insights into the ecological
significance of biofilm microbial communities and to discuss their bioindication potential for water quality and land use
by reporting on 4 years of research performed on the French Ardières-Morcille experimental watershed (AMEW). Various biological
indicators have been applied during several surveys on AMEW, allowing the characterisation of (i) the structure and diversity
of biofilm communities [community level finger printing (CLFP) such as PCR–DGGE and pigment classes], (ii) functions associated
with biofilm [community level physiological profiles (CLPP) such as extracellular enzymes, pesticides biodegradation or carbon
sources biodegradation] and (iii) biofilm tolerance assessment (pollution-induced community tolerance, PICT) of the main contaminant
in the AMEW (copper and diuron). Approaches based on CLFPs and PICT were consistent with each other and indicated the upstream–downstream
impact due to the increasing land use by vineyards and the adaptation of algal and bacterial communities to the pollution
gradient. CLPPs gave a contrasted bioindication because some parameters (most of the tested extracellular enzymes activities)
did not detect a pollution gradient. Such CLPPs, CLFPs and PICT methods applied to biofilm could constitute the basis for
a relevant in situ assessment both for chemical effects and aquatic ecosystem resilience. 相似文献
63.
Michel Lecocq Mathieu Groussin Manolo Gouy Cline Brochier-Armanet 《Molecular biology and evolution》2021,38(5):1761
Previous reports have shown that environmental temperature impacts proteome evolution in Bacteria and Archaea. However, it is unknown whether thermoadaptation mainly occurs via the sequential accumulation of substitutions, massive horizontal gene transfers, or both. Measuring the real contribution of amino acid substitution to thermoadaptation is challenging, because of confounding environmental and genetic factors (e.g., pH, salinity, genomic G + C content) that also affect proteome evolution. Here, using Methanococcales, a major archaeal lineage, as a study model, we show that optimal growth temperature is the major factor affecting variations in amino acid frequencies of proteomes. By combining phylogenomic and ancestral sequence reconstruction approaches, we disclose a sequential substitutional scheme in which lysine plays a central role by fine tuning the pool of arginine, serine, threonine, glutamine, and asparagine, whose frequencies are strongly correlated with optimal growth temperature. Finally, we show that colonization to new thermal niches is not associated with high amounts of horizontal gene transfers. Altogether, although the acquisition of a few key proteins through horizontal gene transfer may have favored thermoadaptation in Methanococcales, our findings support sequential amino acid substitutions as the main factor driving thermoadaptation. 相似文献
64.
Background
Despite a large agreement between ribosomal RNA and concatenated protein phylogenies, the phylogenetic tree of the bacterial domain remains uncertain in its deepest nodes. For instance, the position of the hyperthermophilic Aquificales is debated, as their commonly observed position close to Thermotogales may proceed from horizontal gene transfers, long branch attraction or compositional biases, and may not represent vertical descent. Indeed, another view, based on the analysis of rare genomic changes, places Aquificales close to epsilon-Proteobacteria. 相似文献65.
66.
Valentine SJ Plasencia MD Liu X Krishnan M Naylor S Udseth HR Smith RD Clemmer DE 《Journal of proteome research》2006,5(11):2977-2984
Differential, functional, and mapping proteomic analyses of complex biological mixtures suffer from a lack of component resolution. Here we describe the application of ion mobility-mass spectrometry (IMS-MS) to this problem. With this approach, components that are separated by liquid chromatography are dispersed based on differences in their mobilities through a buffer gas prior to being analyzed by MS. The inclusion of the gas-phase dispersion provides more than an order of magnitude enhancement in component resolution at no cost to data acquisition time. Additionally, the mobility separation often removes high-abundance species from spectral regions containing low-abundance species, effectively increasing measurement sensitivity and dynamic range. Finally, collision-induced dissociation of all ions can be recorded in a single experimental sequence while conventional MS methods sequentially select precursors. The approach is demonstrated in a single, rapid (3.3 h) analysis of a plasma digest sample where abundant proteins have not been removed. Protein database searches have yielded 731 high confidence peptide assignments corresponding to 438 unique proteins. Results have been compiled into an initial analytical map to be used -after further augmentation and refinement- for comparative plasma profiling studies. 相似文献
67.
Role of striatal L-DOPA in the production of dyskinesia in 6-hydroxydopamine lesioned rats 总被引:2,自引:0,他引:2
Carta M Lindgren HS Lundblad M Stancampiano R Fadda F Cenci MA 《Journal of neurochemistry》2006,96(6):1718-1727
We explored possible differences in the peripheral and central pharmacokinetics of L-DOPA as a basis for individual variation in the liability to dyskinesia. Unilaterally, 6-hydroxydopamine (6-OHDA) lesioned rats were treated chronically with L-DOPA for an induction and monitoring of abnormal involuntary movements (AIMs). Comparisons between dyskinetic and non-dyskinetic cases were then carried out with regard to plasma and striatal L-DOPA concentrations, tissue levels of dopamine (DA), DA metabolites, and serotonin. After a single intraperitoneal injection of L-DOPA, plasma L-DOPA concentrations did not differ between dyskinetic and non-dyskinetic animals, whereas peak levels of L-DOPA in the striatal extracellular fluid were about fivefold larger in the former compared with the latter group. Interestingly, the time course of the AIMs paralleled the surge in striatal L-DOPA levels. Intrastriatal infusion of L-DOPA by reverse dialysis concentration dependently induced AIMs in all 6-OHDA lesioned rats, regardless of a previous priming for dyskinesia. Steady-state levels of DA and its metabolites in striatal and cortical tissue did not differ between dyskinetic and non-dyskinetic animals, indicating that the observed difference in motor response to L-DOPA did not depend on the extent of lesion-induced DA depletion. These results show that an elevation of L-DOPA levels in the striatal extracellular fluid is necessary and sufficient for the occurrence of dyskinesia. Individual differences in the central bioavailability of L-DOPA may provide a clue to the varying susceptibility to dyskinesia in Parkinson's disease. 相似文献
68.
Ryan C. Garrick Isabel A. S. Bonatelli Chaz Hyseni Ariadna Morales Tara A. Pelletier Manolo F. Perez Edwin Rice Jordan D. Satler Rebecca E. Symula Maria Tereza C. Thomé Bryan C. Carstens 《Molecular ecology》2015,24(6):1164-1171
Empirical phylogeographic studies have progressively sampled greater numbers of loci over time, in part motivated by theoretical papers showing that estimates of key demographic parameters improve as the number of loci increases. Recently, next‐generation sequencing has been applied to questions about organismal history, with the promise of revolutionizing the field. However, no systematic assessment of how phylogeographic data sets have changed over time with respect to overall size and information content has been performed. Here, we quantify the changing nature of these genetic data sets over the past 20 years, focusing on papers published in Molecular Ecology. We found that the number of independent loci, the total number of alleles sampled and the total number of single nucleotide polymorphisms (SNPs) per data set has improved over time, with particularly dramatic increases within the past 5 years. Interestingly, uniparentally inherited organellar markers (e.g. animal mitochondrial and plant chloroplast DNA) continue to represent an important component of phylogeographic data. Single‐species studies (cf. comparative studies) that focus on vertebrates (particularly fish and to some extent, birds) represent the gold standard of phylogeographic data collection. Based on the current trajectory seen in our survey data, forecast modelling indicates that the median number of SNPs per data set for studies published by the end of the year 2016 may approach ~20 000. This survey provides baseline information for understanding the evolution of phylogeographic data sets and underscores the fact that development of analytical methods for handling very large genetic data sets will be critical for facilitating growth of the field. 相似文献
69.
Manolo D’Arcangelo Matilde Todaro Jessica Salvini Antonina Benfante Maria Luisa Colorito Armida D’Incecco Lorenza Landi Tiziana Apuzzo Elisa Rossi Spartaco Sani Giorgio Stassi Federico Cappuzzo 《PloS one》2015,10(5)
Background
Cancer stem cells represent a population of immature tumor cells found in most solid tumors. Their peculiar features make them ideal models for studying drug resistance and sensitivity. In this study, we investigated whether cancer stem cells isolation and in vitro sensitivity assay are feasible in a clinical setting.Methods
Cancer stem cells were isolated from effusions or fresh cancer tissue of 23 patients who progressed after standard therapy failure. Specific culture conditions selected for immature tumor cells that express markers of stemness. These cells were exposed in vitro to chemotherapeutic and targeted agents.Results
Cancer stem cells were extracted from liver metastases in 6 cases (25%), lung nodules in 2 (8%), lymph node metastases in 3 (12.5%) and pleural/peritoneal/pericardial effusion in 13 (54%). Cancer stem cells were successfully isolated in 15 patients (63%), including 14 with lung cancer (93.3%). A sensitivity assay was successfully performed in 7 patients (30.4%), with a median of 15 drugs/combinations tested (range 5-28) and a median time required for results of 51 days (range 37-95).Conclusion
The approach used for the STELLA trial allowed isolation of cancer stem cells in a consistent proportion of patients. The low percentage of cases completing the full procedure and the long median time for obtaining results highlights the need for a more efficient procedure.Trial Registration
ClinalTrials.gov NCT01483001 相似文献70.
Methods to infer the ancestral conditions of life are commonly based on geological and paleontological analyses. Recently, several studies used genome sequences to gain information about past ecological conditions taking advantage of the property that the G+C and amino acid contents of bacterial and archaeal ribosomal DNA genes and proteins, respectively, are strongly influenced by the environmental temperature. The adaptation to optimal growth temperature (OGT) since the Last Universal Common Ancestor (LUCA) over the universal tree of life was examined, and it was concluded that LUCA was likely to have been a mesophilic organism and that a parallel adaptation to high temperature occurred independently along the two lineages leading to the ancestors of Bacteria on one side and of Archaea and Eukarya on the other side. Here, we focus on Archaea to gain a precise view of the adaptation to OGT over time in this domain. It has been often proposed on the basis of indirect evidence that the last archaeal common ancestor was a hyperthermophilic organism. Moreover, many results showed the influence of environmental temperature on the evolutionary dynamics of archaeal genomes: Thermophilic organisms generally display lower evolutionary rates than mesophiles. However, to our knowledge, no study tried to explain the differences of evolutionary rates for the entire archaeal domain and to investigate the evolution of substitution rates over time. A comprehensive archaeal phylogeny and a non homogeneous model of the molecular evolutionary process allowed us to estimate ancestral base and amino acid compositions and OGTs at each internal node of the archaeal phylogenetic tree. The last archaeal common ancestor is predicted to have been hyperthermophilic and adaptations to cooler environments can be observed for extant mesophilic species. Furthermore, mesophilic species present both long branches and high variation of nucleotide and amino acid compositions since the last archaeal common ancestor. The increase of substitution rates observed in mesophilic lineages along all their branches can be interpreted as an ongoing adaptation to colder temperatures and to new metabolisms. We conclude that environmental temperature is a major factor that governs evolutionary rates in Archaea. 相似文献