A specific genetic background is required for acquisition and expression of virulence factors

In bacteria, the evolution of pathogenicity seems to be the result of the constant arrival of virulence factors (VFs) into the bacterial genome. However, the integration, retention, and/or expression of these factors may be the result of the interaction between the new arriving genes and the bacterial genomic background. To test this hypothesis, a phylogenetic analysis was done on a collection of 98 Escherichia coli/Shigella strains representing the pathogenic and commensal diversity of the species. The distribution of 17 VFs associated to the different E. coli pathovars was superimposed on the phylogenetic tree. Three major types of VFs can be recognized: (1) VFs that arrive and are expressed in different genetic backgrounds (such as VFs associated with the pathovars of mild chronic diarrhea: enteroaggregative, enteropathogenic, and diffusely-adhering E. coli), (2) VFs that arrive in different genetic backgrounds but are preferentially found, associated with a specific pathology, in only one particular background (such as VFs associated with extraintestinal diseases), and (3) VFs that require a particular genetic background for the arrival and expression of their virulence potential (such as VFs associated with pathovars typical of severe acute diarrhea: enterohemorragic, enterotoxigenic, and enteroinvasive E. coli strains). The possibility of a single arrival of VFs by chance, followed by a vertical transmission, was ruled out by comparing the evolutionary histories of some of these VFs to the strain phylogeny. These evidences suggest that important changes in the genome of E. coli have occurred during the diversification of the species, allowing the virulence factors associated with severe acute diarrhea to arrive in the population. Thus, the E. coli genome seems to be formed by an ''ancestral'' and a ''derived'' background, each one responsible for the acquisition and expression of different virulence factors

Data from: Evolutionary dynamics of separate and combined exposure of Pseudomonas fluorescens SBW25 to antibiotics and bacteriophage

The use of bacteriophages against pathogenic bacteria in health care and in the food industry is now being advocated as an alternative to the use of antibiotics. But what is the evolutionary response for a bacterial population if both antibiotics and phages are used in combination? We employ an experimental evolution approach to address these questions and exposed Pseudomonas fluorescens SBW25 and a related hypermutator strain (mutS-) to the action of the antibiotic rifampicin and the lytic bacteriophage SBW25φ2. We then compared the densities, growth rates, and the mutations at the rpoB locus leading to rifampicin resistance of the evolved bacterial populations. We observed that the evolutionary response of populations under different treatments varied depending on the order in which the antimicrobials were added and whether the bacterium was a hypermutator. We found that wild type rifampicin-resistant populations involved in biofilm formation often reverted to rifampicin sensitivity when stresses were added sequentially. In contrast, when the mortality agents were added simultaneously, phage populations frequently went extinct and the bacteria evolved antibiotic resistance. Finally, populations of the hypermutator mutS- converged to a single genotype at the rpoB locus. Future investigation on other bacteria and using different antibiotics and bacteriophage are needed to evaluate the generality of our findings

Selection-driven transcriptome polymorphism in Escherichia coli/Shigella species

To explore the role of transcriptome polymorphism in adaptation of organisms to their environment, we evaluated this parameter for the Escherichia coli/Shigella bacterial species, which is composed of well-characterized phylogenetic groups that exhibit characteristic life styles ranging from commensalism to intracellular pathogenicity. Both the genomic content and the transcriptome of 10 strains representative of the major E. coli/Shigella phylogenetic groups were evaluated using macroarrays displaying the 4290 K12-MG1655 open reading frames (ORFs). Although Shigella and enteroinvasive E. coli (EIEC) are not monophyletic, phylogenetic analysis of the binary coded (presence/absence) gene content data showed that these organisms group together due to similar patterns of undetectable K12-MG1655 genes. The variation in transcript abundance was then analyzed using a core genome of 2880 genes present in all strains, after adjusting RNA hybridization signals for DNA hybridization signals. Nonrandom changes in gene expression during the evolution of the E. coli/Shigella species were evidenced. Phylogenetic analysis of transcriptome data again showed that Shigella and EIEC strains group together in terms of gene expression, and this convergence involved groups of genes displaying biologically coherent patterns of functional divergence. Unlike the other E. coli strains evaluated, Shigella and EIEC are intracellular pathogens, and therefore face similar selective pressures. Thus, within the E. coli/Shigella species, strains exhibiting a particular life style have converged toward a specific gene expression pattern in a subset of genes common to the species, revealing the role of selection in shaping transcriptome polymorphism

A Specific Genetic Background Is Required for Acquisition and Expression of Virulence Factors in Escherichia coli

International audienc

: Commensal Escherichia coli ecological structure

International audienceTo identify forces shaping the Escherichia coli intraspecies ecological structure, we have characterized in terms of phylogenetic group (A, B1, D and B2) belonging, presence/absence of extraintestinal virulence genes (pap, sfa, hly and aer) and intra-host phylotype diversity a collection of 1898 commensal isolates originating from 387 animals (birds and mammals) sampled in the 1980s and the 2000s. These data have been compared with 760 human commensal isolates, sampled from 152 healthy subjects in the 2000s, and analysed with the same approach. The prevalence of the E. coli phylogenetic groups in birds, non-human mammals and humans is clearly different with a predominance of D/B1, A/B1 and A/B2 strains respectively. A major force shaping the ecological structure is the environment with a strong effect of domestication and the year of sampling followed by the climate. Host characteristics, as the diet and body mass, also influence the ecological structure. Human microbiota are characterized by a higher prevalence of virulence genes and a lower intra-host diversity than the non-human mammal ones. This work identifies for the first time a group of strains specific to the animals, the B1 phylogenetic group strains exhibiting the hly gene. In conclusion, a complex network of factors seems to shape the ecological structure of commensal E. coli, with anthropogenic factors playing a major role and perturbing natural niche equilibrium

Evaluación de la Calidad Ambiental, Grado de Optimismo y Asignación de Responsabilidad con Respecto al Estado del Ambiente en Latinoamérica

This study explores the assessments made by the inhabitants of eight Latin American countries regarding the current state of the environment, at a local, national and global scale, and how it is perceived looking ahead to the future. It also examines the assignment of responsibility in the future management of the environment. A total of 944 people took part in the study from the eight participating countries, men and women over the age of 18 with different levels of education. The study uses the Environmental Futures Scale to which two relevant items have been added to assess the environment in the region, as well as the Assignment of Environmental Responsibility Scale. The results show differences between the countries, although in general they are pessimistic regarding the current and future state of the environment at the local, national and global level, with the exception of Brazil. In general, and with the exception of Brazil, in the countries surveyed, people assign a high level of responsibility to external social agents at the different levels, increasing their judgement of external responsibility at the national and global levels of analysis. The implications of these findings for environmental policy and education in the countries of this region are also discussed

Evaluación de la Calidad Ambiental, Grado de Optimismo y Asignación de Responsabilidad con Respecto al Estado del Ambiente en Latinoamérica

This study explores the assessments made by the inhabitants of eight Latin American countries regarding the current state of the environment, at a local, national and global scale, and how it is perceived looking ahead to the future. It also examines the assignment of responsibility in the future management of the environment. A total of 944 people took part in the study from the eight participating countries, men and women over the age of 18 with different levels of education. The study uses the Environmental Futures Scale to which two relevant items have been added to assess the environment in the region, as well as the Assignment of Environmental Responsibility Scale. The results show differences between the countries, although in general they are pessimistic regarding the current and future state of the environment at the local, national and global level, with the exception of Brazil. In general, and with the exception of Brazil, in the countries surveyed, people assign a high level of responsibility to external social agents at the different levels, increasing their judgement of external responsibility at the national and global levels of analysis. The implications of these findings for environmental policy and education in the countries of this region are also discussed.El presente estudio explora las evaluaciones realizadas por los habitantes de ocho países de América Latina en relación con su percepción sobre el estado actual del medio ambiente a escala local, nacional y mundial, así como las expectativas hacia el futuro del ambiente y la asignación de responsabilidades en cuanto a la gestión del futuro ambiental. Participaron un total de 944 personas de ocho países, hombres y mujeres de más 18 años con diferentes niveles de educación. Se aplicó la Escala de Futuros Ambientales a la que se le añadieron dos ítems pertinentes para evaluar el medio ambiente en la región y los ítems correspondientes a la Escala de Responsabilidad Ambiental. Los resultados muestran diferencias entre los países, aunque en general son pesimistas sobre el estado actual y futuro del medio ambiente a nivel local, nacional y mundial, con la excepción de Brasil. Igualmente en general, y con la excepción de Brasil, en los diferentes países encuestados las personas asignan un alto nivel de responsabilidad a los agentes sociales externos en los diferentes niveles, siendo más grande la responsabilidad asignada en los ámbitos nacional y mundial. También se discuten las implicaciones de estos hallazgos para la política del medio ambiente y las implicaciones para la educación en los países de esta región

Assessment of environmental quality, degree of optimism, and the assignment of responsibility regarding the state of the environment in Latin America

This study explores the assessments made by the inhabitants of eight Latin American countries regarding the current state of the environment, at a local, national and global scale, and how it is perceived looking ahead to the future. It also examines the assignment of responsibility in the future management of the environment. A total of 944 people took part in the study from the eight participating countries, men and women over the age of 18 with different levels of education. The study uses the Environmental Futures Scale to which two relevant items have been added to assess the environment in the region, as well as the Assignment of Environmental Responsibility Scale. The results show differences between the countries, although in general they are pessimistic regarding the current and future state of the environment at the local, national and global level, with the exception of Brazil. In general, and with the exception of Brazil, in the countries surveyed, people assign a high level of responsibility to external social agents at the different levels, increasing their judgement of external responsibility at the national and global levels of analysis. The implications of these findings for environmental policy and education in the countries of this region are also discussed

Evaluación de la Calidad Ambiental, Grado de Optimismo y Asignación de Responsabilidad con Respecto al Estado del Ambiente en Latinoamérica

This study explores the assessments made by the inhabitants of eight Latin American countries regarding the current state of the environment, at a local, national and global scale, and how it is perceived looking ahead to the future. It also examines the assignment of responsibility in the future management of the environment. A total of 944 people took part in the study from the eight participating countries, men and women over the age of 18 with different levels of education. The study uses the Environmental Futures Scale to which two relevant items have been added to assess the environment in the region, as well as the Assignment of Environmental Responsibility Scale. The results show differences between the countries, although in general they are pessimistic regarding the current and future state of the environment at the local, national and global level, with the exception of Brazil. In general, and with the exception of Brazil, in the countries surveyed, people assign a high level of responsibility to external social agents at the different levels, increasing their judgement of external responsibility at the national and global levels of analysis. The implications of these findings for environmental policy and education in the countries of this region are also discussed.El presente estudio explora las evaluaciones realizadas por los habitantes de ocho países de América Latina en relación con su percepción sobre el estado actual del medio ambiente a escala local, nacional y mundial, así como las expectativas hacia el futuro del ambiente y la asignación de responsabilidades en cuanto a la gestión del futuro ambiental. Participaron un total de 944 personas de ocho países, hombres y mujeres de más 18 años con diferentes niveles de educación. Se aplicó la Escala de Futuros Ambientales a la que se le añadieron dos ítems pertinentes para evaluar el medio ambiente en la región y los ítems correspondientes a la Escala de Responsabilidad Ambiental. Los resultados muestran diferencias entre los países, aunque en general son pesimistas sobre el estado actual y futuro del medio ambiente a nivel local, nacional y mundial, con la excepción de Brasil. Igualmente en general, y con la excepción de Brasil, en los diferentes países encuestados las personas asignan un alto nivel de responsabilidad a los agentes sociales externos en los diferentes niveles, siendo más grande la responsabilidad asignada en los ámbitos nacional y mundial. También se discuten las implicaciones de estos hallazgos para la política del medio ambiente y las implicaciones para la educación en los países de esta región