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J. Bacteriol. doi:10.1128/JB.00703-08
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Trimeric autotransporters of Haemophilus parasuis: generation of an extensive passenger domain repertoire specific for pathogenic strains

Centre de Recerca en Sanitat Animal (CReSA), UAB-IRTA, Campus de la Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain; Servei de Genòmica. Departament de Bioquímica i Biologia Molecular. Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain; Institut de Recerca i Tecnologia Agroalimentàries (IRTA), Barcelona, Spain

^* To whom correspondence should be addressed. Email: albert.bensaid{at}cresa.uab.es.

	Abstract

Haemophilus parasuis (H. parasuis) is the agent responsible for causing Glässer's disease, but little is known about pathogenic determinants of this major pig disease. Here we describe, for the pathogenic strain Nagasaki, the molecular characterization of 13 trimeric autotransporters as assessed by the presence of YadA C-terminal translocator domains which were classified into three groups. All passenger domains possess motifs and repeats characteristic of adhesins, haemagglutinins and invasins with varying centrally located copies of collagen-like repeats. This domain architecture is shared with two trimeric autotransporter proteins of H. somnus 129 Pt. Genomic comparison by microarray hybridization demonstrated homologies among H. parasuis virulent strains, and high divergence with respect to non-virulent strains. Therefore, these genes were named vtaA (virulence associated trimeric autotransporters). Sequencing of 17 homologous vtaA genes of different invasive strains highlighted an extensive mosaic structure. Based also on the presence of DNA uptake signal sequences (USS) within the vtaA genes, we propose a mechanism of evolution where gene duplication and accumulation of mutations and recombinations, plus lateral gene transfer of the passenger domain, led to the diversity of this multigene family. This study provides insights to help understand tissue colonization and invasiveness characteristic of H. parasuis pathogenic strains.