RESUMO
Aggregatibacter actinomycetemcomitans is implicated in localized aggressive periodontitis. We report the first genome sequence of an A. actinomycetemcomitans strain isolated from an Old World primate.
Assuntos
DNA Bacteriano/química , DNA Bacteriano/genética , Genoma Bacteriano , Pasteurellaceae/genética , Pasteurellaceae/isolamento & purificação , Doenças dos Primatas/microbiologia , Animais , Macaca mulatta , Dados de Sequência Molecular , Infecções por Pasteurellaceae/microbiologia , Infecções por Pasteurellaceae/veterinária , Periodontite/microbiologia , Periodontite/veterinária , Análise de Sequência de DNARESUMO
The Tad (tight adherence) macromolecular transport system, which is present in many bacterial and archaeal species, represents an ancient and major new subtype of type II secretion. The tad genes are present on a genomic island named the widespread colonization island (WCI), and encode the machinery that is required for the assembly of adhesive Flp (fimbrial low-molecular-weight protein) pili. The tad genes are essential for biofilm formation, colonization and pathogenesis in the genera Aggregatibacter (Actinobacillus), Haemophilus, Pasteurella, Pseudomonas, Yersinia, Caulobacter and perhaps others. Here we review the structure, function and evolution of the Tad secretion system.
Assuntos
Actinobacteria/patogenicidade , Aderência Bacteriana , Proteínas de Bactérias , Ilhas Genômicas , Bactérias Gram-Negativas/patogenicidade , Infecções por Actinobacillus/microbiologia , Actinobacteria/genética , Actinobacteria/crescimento & desenvolvimento , Actinobacteria/metabolismo , Aggregatibacter actinomycetemcomitans/genética , Aggregatibacter actinomycetemcomitans/crescimento & desenvolvimento , Aggregatibacter actinomycetemcomitans/metabolismo , Aggregatibacter actinomycetemcomitans/patogenicidade , Animais , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Flagelos/metabolismo , Bactérias Gram-Negativas/genética , Bactérias Gram-Negativas/crescimento & desenvolvimento , Bactérias Gram-Negativas/metabolismo , Humanos , Periodontite/microbiologia , Ratos , Fatores de Virulência/genética , Fatores de Virulência/metabolismoRESUMO
Actinobacillus actinomycetemcomitans is a Gram-negative coccobacillus that has been associated with localized aggressive periodontitis and infections of the heart, brain, and urinary tract. Wild-type clinical isolates have the remarkable ability to adhere tenaciously and nonspecifically to solid surfaces such as glass, plastic, and hydroxyapatite. Adherence by A. actinomycetemcomitans is mediated by the tight-adherence (tad) gene locus, which consists of 14 genes (flp-1-flp-2-tadV-rcpCAB-tadZABCDEFG). All but 2 of the genes have been shown to be required for the secretion and assembly of long, bundled Flp1 fibrils. To test whether the tad locus is required for colonization and disease, we developed a rat model for periodontal disease. To mimic the natural route of infection, Sprague-Dawley rats were inoculated orally by adding bacteria directly to their food for 8 days. After inoculation with wild-type or mutant strains defective in adherence (flp-1 and tadA), the rats were assessed for colonization of the oral cavity and pathogenesis. Wild-type A. actinomycetemcomitans was able to colonize and persist for at least 12 weeks in the oral cavity, elicit a humoral immune response, and cause significant bone loss in rats. In contrast, rats fed flp-1 or tadA mutant strains showed no bone loss and their immune responses were indistinguishable from those of the uninoculated controls. These results demonstrate the critical importance of the tad locus in the colonization and pathogenesis of A. actinomycetemcomitans.