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The capsule biosynthesis locus of Haemophilus influenzae show conspicuous similarity to the corresponding locus in Haemophilus sputorum and may have been recruited from this species by horizontal gene transfer.

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  • Signe Maria Nielsen
  • Camilla de Gier, Department of Clinical Microbiology, Aarhus University Hospital, Denmark
  • Chrysoula Dimopoulou, Denmark
  • Vikas Gupta, Denmark
  • Lars Hestbjerg Hansen, Denmark
  • Niels Nørskov-Lauritsen, Denmark
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 encode 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 open reading frames 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 relatively recently have been recruited from the commensal species H. sputorum by horizontal gene transfer.
Original languageEnglish
Pages (from-to)1182-1188
Number of pages7
Publication statusPublished - 2015

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