Journal article
Comparative genomic analysis identifies X-factor (haemin)-independent Haemophilus haemolyticus: a formal re-classification of 'Haemophilus intermedius'
Microbial genomics, Vol.6(1), 303
2020
Abstract
The heterogeneous and highly recombinogenic genus Haemophilus comprises several species, some of which are pathogenic to humans. All share an absolute requirement for blood-derived factors during growth. Certain species, such as the pathogen Haemophilus influenzae and the commensal Haemophilus haemolyticus, are thought to require both haemin (X-factor) and nicotinamide adenine dinucleotide (NAD, V-factor), whereas others, such as the informally classified 'Haemophilus intermedius subsp. intermedius', and Haemophilus parainfluenzae, only require V-factor. These differing growth requirements are commonly used for species differentiation, although a number of studies are now revealing issues with this approach. Here, we perform large-scale phylogenomics of 240 Haemophilus spp. genomes, including five 'H. intermedius' genomes generated in the current study, to reveal that strains of the 'H. intermedius' group are in fact haemin-independent H. haemolyticus (hiHh). Closer examination of these hiHh strains revealed that they encode an intact haemin biosynthesis pathway, unlike haemin-dependent H. haemolyticus and H. influenzae, which lack most haemin biosynthesis genes. Our results suggest that the common ancestor of modern-day H. haemolyticus and H. influenzae lost key haemin biosynthesis loci, likely as a consequence of specialized adaptation to otorhinolaryngeal and respiratory niches during their divergence from H. parainfluenzae. Genetic similarity analysis demonstrated that the haemin biosynthesis loci acquired in the hiHh lineage were likely laterally transferred from a H. parainfluenzae ancestor, and that this event probably occurred only once in hiHh. This study further challenges the validity of phenotypic methods for differentiating among Haemophilus species, and highlights the need for whole-genome sequencing for accurate characterization of species within this taxonomically challenging genus.
Details
- Title
- Comparative genomic analysis identifies X-factor (haemin)-independent Haemophilus haemolyticus: a formal re-classification of 'Haemophilus intermedius'
- Authors
- Tegan M Harris (Author) - Menzies School of Health ResearchErin P Price (Author) - University of the Sunshine CoastDerek S Sarovich (Author) - University of the Sunshine CoastNiels Norskov-Lauritsen (Author) - Aarhus University Hospital, DenmarkJemima Beissbarth (Author) - Menzies School of Health ResearchAnne B Chang (Author) - Menzies School of Health ResearchHeidi C Smith-Vaughan (Author) - Menzies School of Health Research
- Publication details
- Microbial genomics, Vol.6(1), 303
- Publisher
- Microbiology Society
- Date published
- 2020
- DOI
- 10.1099/mgen.0.000303
- ISSN
- 2057-5858
- Copyright note
- Copyright © 2020 The Authors. This is an open-access article distributed under the terms of the Creative Commons Attribution License.
- Organisation Unit
- University of the Sunshine Coast, Queensland; Centre for Bioinnovation
- Language
- English
- Record Identifier
- 99451337402621
- Output Type
- Journal article
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- Microbiology
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