HlyF Produced by Extraintestinal Pathogenic Escherichia coli Is a Virulence Factor That Regulates Outer Membrane Vesicle Biogenesis.

International audienceEscherichia coli can cause extraintestinal infections in humans and animals. The hlyF gene is epidemiologically associated with virulent strains of avian pathogenic E. coli and human neonatal meningitis-associated E. coli. We demonstrated that culture supernatants of E. coli expressing HlyF induced autophagy in eukaryotic cells. This phenotype coincided with an enhanced production of outer membrane vesicles (OMVs) by bacteria expressing HlyF. The HlyF protein displays a predicted catalytic domain of the short-chain dehydrogenase/reductase superfamily. This conserved domain was involved the ability of HlyF to promote the production of OMVs. The increased production of OMVs was associated with the release of toxins. hlyF was shown to be expressed during extraintestinal infection and to play a role in the virulence of extraintestinal pathogenic E. coli in a chicken model of colibacillosis. This is the first evidence that pathogenic bacteria produce a virulence factor directly involved in the production of OMVs

Capacity of blood plasma is higher in birds breeding in radioactively contaminated areas

Background Environmental pollution in general, and radioactive contamination in particular, may deeply affect host-parasite relationships and their consequences for the evolution of organisms. The nuclear accident that occurred more than 30 years ago in Chernobyl resulted in significant changes in diversity and richness of microbial communities that could influence characteristics of animal-bacteria interactions, including host immune responses and competitive interference by bacteria. Given the high mortality rate of birds breeding in radioactively contaminated zones, those with stronger defences against infections should experience significant fitness advantages. Methodology/Principal Findings Here we characterized antimicrobial capacity of barn swallows (Hirundo rustica) from different Ukrainian populations (subject to a gradient of ionizing radiation) against 12 bacterial species. We also quantified constitutive innate immunity, which is the non-specific first barrier of protection of hosts against microbial parasites. We found a positive association between specific antimicrobial capacity of individual hosts and radiation levels in breeding habitats even after controlling for other confounding variables such as sex and age. However, no significant relationship was found between immunocompetence (non-specific response) and background radiation. Conclusions/Significance These results suggest that radiation selects for broad antimicrobial spectra of barn swallows, although not for all bacterial strains. We discuss these results in the framework of host-parasite evolution under extreme environmental conditions.M. Ruiz-Rodríguez had a postdoc stipend from the program “Andalucía Talent Hub” (Agencia Andaluza del Conocimiento, Junta de Andalucía). Funding was provided in part by the Samuel Freeman Charitable Trust, the US Fulbright Program, the CNRS (France), the American Council of Learned Societies, the University of South Carolina College of Arts and Sciences, and the Spanish Ministerio de Economía y Competitividad (European funds (FEDER)) (CGL2013- 48193-C3-1-P).Peer reviewe