Search results for "Rule"
showing 10 items of 1403 documents
Theoretical conditions for the coexistence of viral strains with differences in phenotypic traits : A bifurcation analysis
2019
We investigate the dynamics of a wild-type viral strain which generates mutant strains differing in phenotypic properties for infectivity, virulence and mutation rates. We study, by means of a mathematical model and bifurcation analysis, conditions under which the wild-type and mutant viruses, which compete for the same host cells, can coexist. The coexistence conditions are formulated in terms of the basic reproductive numbers of the strains, a maximum value of the mutation rate and the virulence of the pathogens. The analysis reveals that parameter space can be divided into five regions, each with distinct dynamics, that are organized around degenerate Bogdanov–Takens and zero-Hopf bifurc…
Mucin induces CRISPR-Cas defense in an opportunistic pathogen
2022
It is unknown what circumstances promote particular bacterial defenses against bacterial viruses (phages). Almeida & Hoikkala et al. show that mucin, derived from mucus, greatly accelerates CRISPR-Cas defenses against phage in an opportunistic pathogen. Parasitism by bacteriophages has led to the evolution of a variety of defense mechanisms in their host bacteria. However, it is unclear what factors lead to specific defenses being deployed upon phage infection. To explore this question, we co-evolved the bacterial fish pathogen Flavobacterium columnare and its virulent phage V156 in presence and absence of a eukaryotic host signal (mucin) for sixteen weeks. The presence of mucin leads to a …
The effect of a temperature-sensitive prophage on the evolution of virulence in an opportunistic bacterial pathogen
2019
AbstractViruses are key actors of ecosystems and have major impacts on global biogeochemical cycles. Prophages deserve particular attention as they are ubiquitous in bacterial genomes and can enter a lytic cycle when triggered by environmental conditions. We explored how temperature affects the interactions between prophages and other biological levels by using an opportunistic pathogen, the bacterium Serratia marcescens, that harbours several prophages and that had undergone an evolution experiment under several temperature regimes. We found that the release of one of the prophages was temperature-sensitive and malleable to evolutionary changes. We further discovered that the virulence of …
Prevalence of genetically similarFlavobacterium columnarephages across aquaculture environments reveals a strong potential for pathogen control
2020
SummaryIntensive aquaculture conditions expose fish to bacterial infections, leading to significant financial losses, extensive antibiotic use and risk of antibiotic resistance in target bacteria.Flavobacterium columnarecauses columnaris disease in aquaculture worldwide. To develop a bacteriophage-based control of columnaris disease, we isolated and characterized 126F. columnarestrains and 63 phages againstF. columnarefrom Finland and Sweden. Bacterial isolates were virulent on rainbow trout (Oncorhynchus mykiss) and fell into four previously described genetic groups A, C, E and G, with genetic groups C and E being the most virulent. Phage host range studied against a collection of 228 bact…
Chapter 12 Role of Iron in Plant–Microbe Interactions
2009
Iron is an essential micronutrient for plants and associated microorganisms. Iron nutrition of these organisms relies on the soil supply. However, bioavailability of iron in cultivated soils is low. Plants and microorganisms have thus evolved active strategies of iron uptake based on acidification, chelation, and/or reduction processes. Iron acquisition by these organisms leads to complex interactions ranging from mutualism to competition. In the rhizosphere, plants support abundant and active microbial communities through the release of rhizodeposits. Iron uptake by these microorganisms and by the host plant decrease even more the concentration of iron in solution. Therefore, there is an i…
Cuestiones varias en torno a la determinación de la filiación por doble paternidad
2018
The article 7.3 of the law 14/2006, of May 26 on technologies of human assisted reproduction establishes the possibility of determining legally the double maternity of married women and not separated legally or of fact, when the not biological mother consents that filiation decides to his favor the respect of the born son of his spouse. In the suppositions not regulated in the mentioned rule the Supreme Court in relation with equal women?s homosexuality in judgment of December 5, 2013 and January 15, 2014 applies the civil code and allows to determine judicially the maternity by means of the exercise of an action of claim for possession of status foreseen in the article 131. In the present …
The Vibrio choleare haemolysin anion channel is required for cell vacuolation and death
2002
SummarySeveral strains of Vibrio cholerae secrete ahaemolytic toxin of 63kDa, termed V. cholerae cytolysin (VCC). This toxin causes extensive vacuo-lation and death of cells in culture and forms ananion-selective channel in planar lipid bilayers and incells. Here, we identify inhibitors of the VCC anionchannel and show that the formation of the anionchannel is necessary for the development of the vacuoles and for the cell death induced by this toxin. Using markers of cell organelles, we show that vacuoles derive from different intracellular com-partments and we identify the contribution of lateendosomes and of the trans -Golgi network in vacuolebiogenesis.Introduction The Gram-negative bact…
What do we mean by diversity? : the path towards quantification
2018
The concept of biological diversity has evolved from a simple count of species to more sophisticated measures that are sensitive to relative abundances and even to evolutionary divergence times between species. In the course of this evolution, diversity measures have often been borrowed from other disciplines. Biological reasoning about diversity often implicitly assumed that measures of diversity had certain mathematical properties, but most of biologys traditional diversity measures did not actually possess these properties, a situation which often led to mathematically and biologically invalid inferences. Biologists now usually transform the traditional measures to the «effective number …
Field rules and bias in random surveys with quota samples : an assessment of CIS surveys
2018
Surveys applying quota sampling in their final step are widely used in opinion and market research all over the world. This is also the case in Spain, where the surveys carried out by CIS (a public institution for sociological research supported by the government) have become a point of reference. The rules used by CIS to select individuals within quotas, however, could be improved as they lead to biases in age distributions. Analysing more than 545,000 responses collected in the 220 monthly barometers conducted between 1997 and 2016 by CIS, we compare the empirical distributions of the barometers with the expected distributions from the sample design and/or target populations. Among other …
La incidencia de las malas relaciones entre los progenitores a la hora de acordar el régimen de guarda y custodia compartida. Análisis de la reciente…
2018
The relationship that the parents have with each other is one of the factors to take into consideration when adopting or not the modality of shared custody and custody after a situation of family crisis. To deny the shared modality if there was no good relationship between the parents was the rule until relatively recent dates. With the entry into force of local laws as well as the change in jurisprudence, the tendency that remains is to consider that it will no longer be enough that there is this bad relationship but will have to be a situation of high confrontation so that this situation may be grounds for denial of the shared custody regime.