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Multilayer Polyelectrolyte Films Functionalized by Insertion of Defensin: a New Approach to Protection of Implants from Bacterial Colonization. O. Etienne, 2004.Infection of implanted materials by bacteria constitutes one of the most serious complications following prosthetic surgery . In the present study, we developed a new strategy based on the insertion of an antimicrobial peptide (defensin from Anopheles gambiae mosquitoes) into polyelectrolyte multilayer films built by the alternate deposition of polyanions and polycations . Quartz crystal microbalance and streaming potential measurements were used to follow step by step the construction of the multilayer films and embedding of the defensin within the films . Antimicrobial assays were performed with two strains: Micrococcus luteus (a gram-positive bacterium) and Escherichia coli D22 (a gram-negative bacterium) . The inhibition of E . coli D22 growth at the surface of defensin-functionalized films was found to be 98% when 10 antimicrobial peptide layers were inserted in the film architecture . Noticeably, the biofunctionalization could be achieved only when positively charged poly(L-lysine) was the outermost layer of the film . On the basis of the results of bacterial adhesion experiments observed by confocal or electron microscopy, these observations could result from the close interaction of the bacteria with the positively charged ends of the films, which allows defensin to interact with the bacterial membrane structure . These results open new possibilities for the use of such easily built and functionalized architectures onto any type of implantable biomaterial . The modified surfaces are active against microbial infection and represent a novel means of local host protection . Genome Differences That Distinguish Bacillus anthracis from Bacillus cereus and Bacillus thuringiensis. Lyndsay Radnedge, 2003.The three species of the group 1 bacilli, Bacillus anthracis, B . cereus, and B . thuringiensis, are genetically very closely related . All inhabit soil habitats but exhibit different phenotypes . B . anthracis is the causative agent of anthrax and is phylogenetically monomorphic, while B . cereus and B . thuringiensis are genetically more diverse . An amplified fragment length polymorphism analysis described here demonstrates genetic diversity among a collection of non-anthrax-causing Bacillus species, some of which show significant similarity to B . anthracis . Suppression subtractive hybridization was then used to characterize the genomic differences that distinguish three of the non-anthrax-causing bacilli from B . anthracis Ames . Ninety-three DNA sequences that were present in B . anthracis but absent from the non-anthrax-causing Bacillus genomes were isolated . Furthermore, 28 of these sequences were not found in a collection of 10 non-anthrax-causing Bacillus species but were present in all members of a representative collection of B . anthracis strains . These sequences map to distinct loci on the B . anthracis genome and can be assayed simultaneously in multiplex PCR assays for rapid and highly specific DNA-based detection of B . anthracis .
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