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The Burkholderia cepacia rpoE gene is not involved in exopolysaccharide production and onion pathogenicity

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Burkholderia cepacia was originally described as the causative agent of bacterial rot of onions, and it has now emerged as an important opportunistic pathogen causing severe chronic lung infections in patients having cystic fibrosis. Burkholderia cepacia is now classified into nine very closely related species (previously designated as genomovars), all of which have been isolated from both environmental and clinical sources and are collectively known as the B. cepacia complex. The alternative extracytoplasmic function  factor, E, has been determined in several bacterial species as making substantial contributions to bacterial survival under stress conditions. Here, we report the identification and characterization of the rpoE gene, encoding E, of B. cepacia. It is highly similar to E of other bacteria, including Escherichia coli and Pseudomonas aeruginosa. Studies using an rpoE knockout mutant of B. cepacia revealed that many stress adaptations, including osmotic, oxidative, desiccation, carbon, and nitrogen stress, were independent of E. Similarly, biofilm formation; production of exopolysaccharides, N-acyl homoserine lactones, and several exoenzymes; and onion pathogenicity were not affected by the absence of E. In contrast, E contributed to the adaptation to heat stress and phosphate starvation.Key words: Burkholderia cepacia, sigma factor, rpoE, extracytoplasmic function.

Burkholderia cepacia fut originellement décrit comme étant l'agent causant la pourriture bactérienne de l'oignon et est maintenant considéré comme étant un important pathogène opportuniste émergeant causant des infections pulmonaires chroniques graves chez des patients souffrant de fibrose kystique. Burkholderia cepacia est désormais classifié en neuf espèces fortement apparentées (préalablement désignés en tant que génomovars) qui ont toutes été isolées de sources environnementales ou cliniques et sont désignées dans leur ensemble en tant que complexe B. cepacia. Les contributions extracytoplasmiques alternatives à la survie bactérienne dans des conditions de stress. Nous faisons ici état de l'identification et de la caractérisation du gène rpoE, codant E, de B. cepacia. Il est fortement semblable à E d'autres bactéries incluant Escherichia coli et Pseudomonas aeruginosa. Les études utilisant un mutant knock-out rpoE de B. cepacia ont révélé que plusieurs adaptations au stress, incluant le stress osmotique, oxydatif, le dessèchement, le carbone et le stress à l'azote étaient indépendantes de E. De même, la formation de biofilms, la production d'exopolysaccharides, la production de N-acyl homosérine lactones, la production de plusieurs exo-enzymes et la pathogénicité envers l'oignon n'ont pas été affectés par l'absence de E. En revanche, E a contribué à l'adaptation au stress thermique et à la carence en phosphate.Mots clés : Burkholderia cepacia, facteur sigma, rpoE, fonction extracytoplasmique.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: March 1, 2006

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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