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Phosphatidylcholine in membrane of Escherichia coli changes bacterial antigenicity

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This study reports that Escherichia coli phosphatidylcholine-positive (PC+) strain Top10/ptac66 (PC+ PE+), in which borrelial PC synthase (PCS) directly condenses exogenous choline with CDP-diacylglycerol (CDP-DAG) to form PC, displayed not only stronger resistance to antimicrobial peptides cecropin P1 and indolicidin, but also decreased ability to attract macrophages to the abdominal cavity of infected mice in the 36 h following infection, compared with the control strainTop10/ptac85 (PC- PE+). Rabbit sera raised against the PC+ strains Top10/ptac66 (PC+ PE+) and AD93/ptac67 (PC+ PE-) recognized a different set of periplasmic proteins and lipopolysaccharides,compared with those detected by antisera to the PC- strains Top10/ptac85 and AD93 (PC- PE-) . Electron microscopy also showed that the morphology of cell wall of Top10/ptac66 was different from that of the control strain Top10/ptac85. Enhancement of bacterial resistance to antimicrobe peptides, alteration of bacterial antigenicity and evasion of macrophage attacks in mice suggest that PC in the bacterial membrane may play a role in bacterial evasion of the innate or adaptive immune response of the host.

Cette étude rapporte que les souches d’Escherichia coli PC+ Top10/ptac66 (PC+PE+), dans lesquelles la phosphatidiyl synthase de Borrelia (PCS) condense directement la choline exogène au CDP-diacylglycérol (CDP-DAG) pour former la PC, montrent non seulement une résistance plus élevée envers la cécropine P1 et l’indolicidine, deux peptides antimicrobiens (PAM), mais montrent également une capacité diminuée d’attirer les macrophages de la cavité abdominale de souris infectées dans les 36 premières h suivant l’infection, comparativement à la souche contrôle Top10/ptac85 (PC- PE+). Des sérums de lapins immunisés contre les souches PC+ Top10/ptac66 (PC+ PE+) et AD93/ptac67 (PC+ PE-) reconnaissaient un ensemble différent de protéines périplasmiques et de lipopolysaccharides (LPS), comparativement aux anti-sérums dirigés contre les souches PC- Top10/ptac85 et AD93 (PC- PE-). La microscopie électronique a aussi montré que la morphologie de la paroi cellulaire de Top10/ptac66 était différente de celle de la souche contrôle Top10/ptac85. L’augmentation de la résistance bactérienne aux peptides antimicrobiens, le changement de l’antigénicité bactérienne et l’évasion face aux attaques des macrophages chez la souris suggèrent que la PC de la membrane bactérienne peut peut-être jouer un rôle dans l’évasion bactérienne lors des réponses immunitaires innée ou adaptative de l’hôte.

Document Type: Research Article

Publication date: November 1, 2009

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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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