title: The capsule biosynthesis locus of Haemophilus influenzae shows conspicuous similarity to the corresponding locus in Haemophilus sputorum and may have been recruited from this species by horizontal gene transfer.
abstract: The newly described species Haemophilus sputorum has been cultured from the upper respiratory tract of humans and appears to have little pathogenic potential. The species encodes a capsular biosynthesis locus of approximately 12  kb composed of three distinct regions. Region I and III genes, involved in export and processing of the capsular material, show high similarity to the corresponding genes in capsulate lineages of the pathogenic species Haemophilus influenzae; indeed, standard bexA and bexB PCRs for detection of capsulated strains of H. influenzae give positive results with strains of H. sputorum. Three ORFs are present in region II of the sequenced strain of H. sputorum, of which a putative phosphotransferase showed homology with corresponding genes from H. influenzae serotype c and f. Phylogenetic analysis of housekeeping genes from 24 Pasteurellaceae species showed that H. sputorum was only distantly related to H. influenzae. In contrast to H. influenzae, the capsule locus in H. sputorum is not associated with transposases or other transposable elements. Our data suggest that the capsule locus of capsulate lineages of H. influenzae may have been recruited relatively recently from the commensal species H. sputorum by horizontal gene transfer.
authors: 1Department of Clinical Microbiology, Aarhus University Hospital, Aarhus, Denmark.
authors: Signe M
authors: SM
authors: Nielsen
authors: 1Department of Clinical Microbiology, Aarhus University Hospital, Aarhus, Denmark.
authors: Camilla
authors: C
authors: de Gier
authors: 2Department of Environmental Science, Aarhus University, Roskilde, Denmark.
authors: Chrysoula
authors: C
authors: Dimopoulou
authors: 3Bioinformatics Research Centre, Aarhus University, Aarhus, Denmark.
authors: Vikas
authors: V
authors: Gupta
authors: 2Department of Environmental Science, Aarhus University, Roskilde, Denmark.
authors: Lars H
authors: LH
authors: Hansen
authors: 1Department of Clinical Microbiology, Aarhus University Hospital, Aarhus, Denmark.
authors: Niels
authors: N
authors: Nørskov-Lauritsen
mesh_terms: D016667:Bacterial Capsules / Q000235:genetics*; D019143:Evolution, Molecular; D023061:Gene Order; D022761:Gene Transfer, Horizontal; D020043:Genes, Essential; D056426:Genetic Loci; D006190:Haemophilus / Q000235:genetics*; D006192:Haemophilus Infections / Q000382:microbiology; D006801:Humans; D053858:Metabolic Networks and Pathways / Q000235:genetics*; D016366:Open Reading Frames; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012141:Respiratory Tract Infections / Q000382:microbiology; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D026801:Synteny