title: Evidence for an intact polysaccharide capsule in Bordetella pertussis.
abstract: Polysaccharide capsules contribute to the pathogenesis of many bacteria species by providing resistance against various defense mechanisms. The production of a capsule in Bordetella pertussis, the etiologic agent of whooping cough, has remained controversial; earlier studies reported this pathogen as a capsulated microorganism whereas the recent B. pertussis genome analysis revealed the presence of a truncated capsule locus. In this work, using transmission electron microscopy and immunostaining approaches, we provide a formal evidence for the presence of an intact microcapsule produced at the surface of both laboratory strain and clinical isolates of B. pertussis. In agreement with previous studies, we found that the capsule is optimally produced in avirulent phase. Unexpectedly, the presence of the capsule was also detected at the surface of virulent B. pertussis bacteria. Consistently, a substantial transcriptional activity of the capsule operon was detected in virulent phase, suggesting that the capsular polysaccharide may play a role during pertussis pathogenesis. In vitro assays indicated that the presence of the capsule does not affect B. pertussis adherence to mammalian cells and does not further protect the bacterium from phagocytosis, complement-mediated killing or antimicrobial peptide attack.
authors.affiliation: Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, CeLS building # 03-05, 28 Medical Drive, Singapore 117597, Singapore.
authors.forename: YiLin
authors.initials: Y
authors.lastname: Neo
authors.forename: Rui
authors.initials: R
authors.lastname: Li
authors.forename: Josephine
authors.initials: J
authors.lastname: Howe
authors.forename: Regina
authors.initials: R
authors.lastname: Hoo
authors.forename: Aakanksha
authors.initials: A
authors.lastname: Pant
authors.forename: SiYing
authors.initials: S
authors.lastname: Ho
authors.forename: Sylvie
authors.initials: S
authors.lastname: Alonso
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion; D016667:Bacterial Capsules / Q000032:analysis* / Q000648:ultrastructure*; D001886:Bordetella pertussis / Q000737:chemistry / Q000502:physiology* / Q000648:ultrastructure; D002460:Cell Line; D003165:Complement System Proteins / Q000276:immunology; D004847:Epithelial Cells / Q000382:microbiology; D006801:Humans; D007150:Immunohistochemistry; D008264:Macrophages / Q000276:immunology; D051379:Mice; D050296:Microbial Viability; D046529:Microscopy, Electron, Transmission; D010587:Phagocytosis
chemical_list: D003165:Complement System Proteins