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Identification of Streptococcus pneumoniae genes specifically induced in mouse lung tissues

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To identify Streptococcus pneumoniae genes expressed specifically during infections, a selection system based on the in vivo expression technology (IVET) was established. galU, which is critical for capsular polysaccharide biosynthesis, and lacZY encoding -galactosidase were employed as dual reporter genes to screen in-vivo-induced (ivi) genes of S.pneumoniae. The galU-deficient mutant of S.pneumoniae is incapable of utilizing galactose, thus failing to synthesize capsular polysaccharide, and therefore loses its ability to survive in the host. A promoter-trap library was constructed in S.pneumoniae, which was used to infect BALB/c mice in an intranostril model. Those strains recovered from lung tissue of mice and exhibiting a white colony phenotype on tryptic soy agar containing X-gal (5-bromo-4-chloro-3-indolyl---galactopyranoside) were collected and identificated. A total of 15 unique sequences were obtained through in vivo screening. The ivi genes of S.pneumoniae are involved in many processes, such as colonization and adherence, energy metabolism, nutrient substance transport, transcription regulation, DNA metabolism, and cell wall synthesis. There are some hypothetical proteins whose functions are not clear. This novel IVET is a useful tool for identifying ivi genes in S.pneumoniae.

Un système de sélection basé sur la technologie d’expression in vivo (IVET) a été établi afin d’identifier les gènes de Streptococcus pneumoniae exprimés spécifiquement durant les infections. Le gène galU, critique à la biosynthèse du polysaccharide capsulaire, et le gène lacZY qui code la -galactosidase ont été employés comme doubles gènes rapporteurs pour identifier les gènes induits in vivo (ivi) chez S. pneumoniae. Le mutant de S.pneumoniae déficient en galU ne peut utiliser le galactose, étant ainsi incapable de synthétiser le polysaccharide de la capsule et perdant alors sa capacité de survivre à l’intérieur de l’hôte. Une banque d’expression (promoter-trap) a été construite chez S.pneumoniae et a servi à infecter des souris BALB/c dans un modèle intranasal. Les souches récupérées du tissu pulmonaire des souris et présentant un phénotype de colonies blanches sur gélose TSA comprenant du X-gal (5-bromo-4-chloro-3-indolyl---galactopyranoside) ont été prélevées et identifiées. Un total de 15 séquences uniques ont été obtenues par ce criblage in vivo. Les gènes ivi de S.pneumoniae sont impliqués dans plusieurs processus comme la colonisation et l’adhérence, le métabolisme énergétique, le transport de substances nutritives, la régulation de la transcription, le métabolisme de l’ADN et la synthèse de la paroi cellulaire. Il existe aussi des protéines hypothétiques dont les fonctions ne sont pas claires. Cet IVET nouveau est un outil pratique pour identifier des gènes induits in vivo chez S. pneumoniae.

Document Type: Research Article

Publication date: 2008-01-01

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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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