Divergent evolution and purifying selection of the flaA gene sequences in Aeromonas

BACKGROUND: The bacterial flagellum is the most important organelle of motility in bacteria and plays a key role in many bacterial lifestyles, including virulence. The flagellum also provides a paradigm of how hierarchical gene regulation, intricate protein-protein interactions and controlled protein secretion can result in the assembly of a complex multi-protein structure tightly orchestrated in time and space. As if to stress its importance, plants and animals produce receptors specifically dedicated to the recognition of flagella. Aside from motility, the flagellum also moonlights as an adhesion and has been adapted by humans as a tool for peptide display. Flagellar sequence variation constitutes a marker with widespread potential uses for studies of population genetics and phylogeny of bacterial species. RESULTS: We sequenced the complete flagellin gene (flaA) in 18 different species and subspecies of Aeromonas. Sequences ranged in size from 870 (A. allosaccharophila) to 921 nucleotides (A. popoffii). The multiple alignment displayed 924 sites, 66 of which presented alignment gaps. The phylogenetic tree revealed the existence of two groups of species exhibiting different FlaA flagellins (FlaA1 and FlaA2). Maximum likelihood models of codon substitution were used to analyze flaA sequences. Likelihood ratio tests suggested a low variation in selective pressure among lineages, with an omega ratio of less than 1 indicating the presence of purifying selection in almost all cases. Only one site under potential diversifying selection was identified (isoleucine in position 179). However, 17 amino acid positions were inferred as sites that are likely to be under positive selection using the branch-site model. Ancestral reconstruction revealed that these 17 amino acids were among the amino acid changes detected in the ancestral sequence. CONCLUSION: The models applied to our set of sequences allowed us to determine the possible evolutionary pathway followed by the flaA gene in Aeromonas, suggesting that this gene have probably been evolving independently in the two groups of Aeromonas species since the divergence of a distant common ancestor after one or several episodes of positive selection. REVIEWERS: This article was reviewed by Alexey Kondrashov, John Logsdon and Olivier Tenaillon (nominated by Laurence D Hurst).

Draft genome sequence of the Aeromonas diversa type strain

We present here the first genome sequence of the Aeromonas diversa type strain (CECT 4254T). This strain was isolated from the leg wound of a patient in New Orleans (Louisiana, USA) and was originally described as Enteric Group 501 and distinguished from A. schubertii by DNADNA hybridization and phenotypical characterization.

Els treballs filològics de l'acadèmic Josep de Bastero

Sobre els treballs filològics de l'acadèmic Josep Gaspar de Bastero i Vilana que fou membre de la Reial Acadèmia de Bones Lletres des del 1752 fins al 1786, data de la seva mort

Alteritzar la singularitat: veus per a una pedagogia de l'experiència

Parte de la investigación en torno a la realidad educativa que se ha desarrollado durante los últimos años se caracteriza por intentar encontrar formas de interpretación orientadas a significar los procesos formativos centrados en las vivencias singulares de los agentes que participan de la educación así como en la posibilidad que éstas ofrecen de devenir experiencia, eso es,vivencia concienciada. A raíz de las mismas podemos observar como la biografía apunta a ser una de las más emblemáticas formalizaciones del proceso de narración de vivencias. Pero, aún cuando la misma se perfila como una de las narraciones que más promueven la interpretación e intercambio de vivencias, posibilitando la reflexión e, incluso, formación mediada, la biografía todavía presenta como forma teorética algunos escollos. Los cuales, pueden ser utilizados como preguntas base para formular una voz de las pedagogías de la experiencia. Justamente, interrogarse y repensar su factibilidad es el tema que se ensaya en el presente artículo.

Educación musical intercultural a través de un proyecto europeo Comenius y su aportación a las competencias básicas

La experiencia se enmarca en un proyecto de intercambio Comenius desarrollado entre los años 2002-2005, con la participación de seis centros europeos. A partir de la asignatura de prácticas de los alumnos de la Universidad de Girona, se ha implicado la educación musical en el proyecto y se ha desarrollado, a lo largo de tres cursos, una rica experiencia intercultural a través de la canción, la danza y la composición. A su vez, se analizan las aportaciones del proyecto al trabajo de las competencias básicas de la etapa

Full instability behavior of N-dimensional dynamical systems with a one-directional nonlinear vector field

We show how certain N-dimensional dynamical systems are able to exploit the full instability capabilities of their fixed points to do Hopf bifurcations and how such a behavior produces complex time evolutions based on the nonlinear combination of the oscillation modes that emerged from these bifurcations. For really different oscillation frequencies, the evolutions describe robust wave form structures, usually periodic, in which selfsimilarity with respect to both the time scale and system dimension is clearly appreciated. For closer frequencies, the evolution signals usually appear irregular but are still based on the repetition of complex wave form structures. The study is developed by considering vector fields with a scalar-valued nonlinear function of a single variable that is a linear combination of the N dynamical variables. In this case, the linear stability analysis can be used to design N-dimensional systems in which the fixed points of a saddle-node pair experience up to N21 Hopf bifurcations with preselected oscillation frequencies. The secondary processes occurring in the phase region where the variety of limit cycles appear may be rather complex and difficult to characterize, but they produce the nonlinear mixing of oscillation modes with relatively generic features