Search results for "Evolution"
showing 10 items of 11096 documents
Experimental evolution of an RNA virus in cells with innate immunity defects
2015
Experimental evolution studies have shown that RNA viruses respond rapidly to directional selection and thus can adapt efficiently to changes in host cell tropism, antiviral drugs, or other imposed selective pressures. However, the evolution of RNA viruses under relaxed selection has been less extensively explored. Here, we evolved vesicular stomatitis virus in mouse embryonic fibroblasts knocked-out for PKR, a protein with a central role in antiviral innate immunity. Vesicular stomatitis virus adapted to PKR-negative mouse embryonic fibroblasts in a gene-specific manner, since the evolved viruses exhibited little or no fitness improvement in PKR-positive cells. Full-length sequencing revea…
Evidence for Positive Selection in the Capsid Protein-Coding Region of the Foot-and-Mouth Disease Virus (FMDV) Subjected to Experimental Passage Regi…
2001
We present sequence data from two genomic regions of foot-and-mouth disease virus (FMDV) subjected to several experimental passage regimens. Maximum-likelihood estimates of the nonsynonymous-to-synonymous rate ratio parameter (dN/dS) suggested the action of positive selection on some antigenic sites of the FMDV capsid during some experimental passages. These antigenic sites showed an accumulation of convergent amino acid replacements during massive serial cytolytic passages and also in persistent infections of FMDV in cell culture. This accumulation was most significant at the antigenic site A (the G-H loop of capsid VP1), which includes an Arg-Gly-Asp (RGD) cellular recognition motif. Our …
When earwig mothers do not care to share: Parent–offspring competition and the evolution of family life
2017
Kin competition often reduces – and sometimes entirely negates – the benefits of cooperation among family members. Surprisingly, the impact of kin competition on the fitness effects of family life only received close scrutiny in studies on sibling rivalry, whereas the possibility of parent–offspring competition has attracted much less attention. As a consequence, it remains unclear whether and how parent–offspring competition could have affected the early evolution of parental care and family life. Here, we examined the occurrence and consequences of parent–offspring competition over food access in the European earwig Forficula auricularia, an insect with facultative family life reminiscent…
Open-source QCD analysis of nuclear parton distribution functions at NLO and NNLO
2019
We present new sets of nuclear parton distribution functions (nPDFs) at next-to-leading order (NLO) and next-to-next-to-leading order (NNLO). Our analyses are based on deeply inelastic scattering data with charged-lepton and neutrino beams on nuclear targets. In addition, a set of proton baseline PDFs is fitted within the same framework with the same theoretical assumptions. The results of this global QCD analysis are compared to existing nPDF sets and to the fitted cross sections. Also, the uncertainties resulting from the limited constraining power of the included experimental data are presented. The published work is based on an open-source tool, xFitter, which has been modified to be ap…
La difficile instauration du partenariat dans le secteur du bâtiment et des travaux publics: une analyse par les mécanismes de contrôle
1999
From an empirical study on one firm with network type organizational structure, this article explains the configurations of control in the coordination of partners. Investigations on the implemented control system have specified risks and control mechanisms associated to the levels of the networking development. This work shows that two different shapes of control are in use within one organization. Control is transactional-oriented between institutions and relational-oriented between individuals.
Genomic evolution of bacterial populations under co-selection by antibiotics and phage
2017
Bacteria live in dynamic systems where selection pressures can alter rapidly, forcing adaptation to the prevailing conditions. In particular, bacteriophages and antibiotics of anthropogenic origin are major bacterial stressors in many environments. We previously observed that populations of the bacterium Pseudomonas fluorescens SBW25 exposed to the lytic bacteriophage SBW25Φ2 and a noninhibitive concentration of the antibiotic streptomycin (coselection) achieved higher levels of phage resistance compared to populations exposed to the phage alone. In addition, the phage became extinct under coselection while remaining present in the phage alone environment. Further, phenotypic tests indicate…
Fight evolution with evolution: plasmid‐dependent phages with a wide host range prevent the spread of antibiotic resistance
2013
The emergence of pathogenic bacteria resistant to multiple antibiotics is a serious worldwide public health concern. Whenever antibiotics are applied, the genes encoding for antibiotic resistance are selected for within bacterial populations. This has led to the prevalence of conjugative plasmids that carry resistance genes and can transfer themselves between diverse bacterial groups. In this study, we investigated whether it is feasible to attempt to prevent the spread of antibiotic resistances with a lytic bacteriophage, which can replicate in a wide range of gram‐negative bacteria harbouring conjugative drug resistance–conferring plasmids. The counter‐selection against the plasmid was sh…
Dataset for Mucin induces CRISPR-Cas defense in an opportunistic pathogen
2022
This dataset contains raw data points of (1) phage-bacterium co-evolution experiment (flavobacterium columnare colony counts, phage counts, bacterial growth characteristics and number of CRISPR-Cas spacers) and (2) from competition experiment between Flavobacterium columnare and Aeromonas sp. For detailed method description, see the attached Documentation file.
Beneficial coinfection can promote within-host viral diversity
2018
Abstract In many viral infections, a large number of different genetic variants can coexist within a host, leading to more virulent infections that are better able to evolve antiviral resistance and adapt to new hosts. But how is this diversity maintained? Why do faster-growing variants not outcompete slower-growing variants, and erode this diversity? One hypothesis is if there are mutually beneficial interactions between variants, with host cells infected by multiple different viral genomes producing more, or more effective, virions. We modelled this hypothesis with both mathematical models and simulations, and found that moderate levels of beneficial coinfection can maintain high levels o…
Sobre la naturalización de la lógica*
2003
El presente artículo se ocupa de dar razones en contra de la naturalización de la lógica, en tanto en cuanto esto signifique una revisión de esta ciencia. El trabajo critica cada uno de los intentos históricos importantes que ha habido de revisión de las leyes lógicas -- intuicionismo, lógica cuántica, lógicas alternativas - y también intenta argumentar que el problema de la interpretación de la mecánica cuántica no tiene nada que ver con la naturalización de la lógica. This article is devoted to give reasons against the naturalization of logic, in a sense which entails a revision of this science. The paper criticizes each historical important attempt to revise logical laws - intuitionism, …