title: The Autotransporter BpaB Contributes to the Virulence of Burkholderia mallei in an Aerosol Model of Infection.
abstract: Burkholderia mallei is a highly pathogenic bacterium that causes the zoonosis glanders. Previous studies indicated that the genome of the organism contains eight genes specifying autotransporter proteins, which are important virulence factors of Gram-negative bacteria. In the present study, we report the characterization of one of these autotransporters, BpaB. Database searches identified the bpaB gene in ten B. mallei isolates and the predicted proteins were 99-100% identical. Comparative sequence analyses indicate that the gene product is a trimeric autotransporter of 1,090 amino acids with a predicted molecular weight of 105-kDa. Consistent with this finding, we discovered that recombinant bacteria expressing bpaB produce a protein of ≥ 300-kDa on their surface that is reactive with a BpaB-specific monoclonal antibody. Analysis of sera from mice infected with B. mallei indicated that animals produce antibodies against BpaB during the course of disease, thus establishing production of the autotransporter in vivo. To gain insight on its role in virulence, we inactivated the bpaB gene of B. mallei strain ATCC 23344 and determined the median lethal dose of the mutant in a mouse model of aerosol infection. These experiments revealed that the bpaB mutation attenuates virulence 8-14 fold. Using a crystal violet-based assay, we also discovered that constitutive production of BpaB on the surface of B. mallei promotes biofilm formation. To our knowledge, this is the first report of a biofilm factor for this organism.
authors.affiliation: Department of Infectious Diseases, University of Georgia College of Veterinary Medicine, Athens, Georgia, United States of America.
authors.forename: Shawn M
authors.initials: SM
authors.lastname: Zimmerman
authors.affiliation: Department of Veterinary Biosciences and Diagnostic Imaging, University of Georgia College of Veterinary Medicine, Athens, GA, United States of America.
authors.forename: Frank
authors.initials: F
authors.lastname: Michel
authors.affiliation: Department of Infectious Diseases, University of Georgia College of Veterinary Medicine, Athens, Georgia, United States of America; Department of Veterinary Biosciences and Diagnostic Imaging, University of Georgia College of Veterinary Medicine, Athens, GA, United States of America.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Hogan
authors.affiliation: Department of Infectious Diseases, University of Georgia College of Veterinary Medicine, Athens, Georgia, United States of America.
authors.forename: Eric R
authors.initials: ER
authors.lastname: Lafontaine
mesh_terms: D000336:Aerosols; D000818:Animals; D000907:Antibodies, Bacterial / Q000737:chemistry; D000911:Antibodies, Monoclonal / Q000737:chemistry; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D018441:Biofilms / Q000254:growth & development*; D042726:Burkholderia mallei / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity*; D002460:Cell Line; D003001:Cloning, Molecular; D004847:Epithelial Cells / Q000382:microbiology / Q000473:pathology; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005260:Female; D017353:Gene Deletion; D015870:Gene Expression; D005896:Glanders / Q000382:microbiology* / Q000401:mortality / Q000473:pathology / Q000635:transmission; D006801:Humans; D008264:Macrophages / Q000382:microbiology / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D016019:Survival Analysis; D000069320:Type V Secretion Systems / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014774:Virulence
chemical_list: D000336:Aerosols; D000907:Antibodies, Bacterial; D000911:Antibodies, Monoclonal; D001426:Bacterial Proteins; D011994:Recombinant Proteins; D000069320:Type V Secretion Systems