Description of Bartonella bennetti sp. nov., a novel rodent-associated species, with comparative genomics of the Bartonella genus

Brierley, S, Mackenzie, L, Telfer, S, Bown, K ORCID: 0000-0002-9312-7224, Goodhead, I and Birtles, R (2026) Description of Bartonella bennetti sp. nov., a novel rodent-associated species, with comparative genomics of the Bartonella genus. International Journal of Systematic and Evolutionary Microbiology, 76 (3). ISSN 1466-5026

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Abstract

The genus Bartonella comprises over 40 species, most of which are haemoparasites of mammals. Herein, we describe Bartonella bennetti sp. nov., a novel member of the genus, isolated from field voles (Microtus agrestis) in Kielder Forest, UK. Polyphasic characterization of three strains (C271T, D105 and J117) of the proposed species indicated that they were closely related to members of phylogenetic lineage 3 (L3) of the genus. The average nucleotide identity (ANI) between C271T and other L3 species ranged between 88.8 and 90.6%, supporting the proposal of a new species. C271T shared ANIs approaching 96% with other members of L3 that are yet to be validly published but exhibited marked genomic, ecological and biogeographical differences from them, further justifying the creation of a new taxon. All three B. bennetti sp. nov. strains were found to possess genes encoding three VirB/D4 type IV secretion systems and associated effector proteins and to harbour a chromosomally integrated F-type conjugative plasmid, which forms an Hfr-like configuration not previously observed in the Bartonella genus. This integration could facilitate large-scale chromosomal gene transfer during conjugation, with potential consequences for adaptation, recombination and niche differentiation. The phylogenetic structure of L3, coupled with the ecological partitioning of its members, suggests that covert host specificity, not generalism, is the dominant mode of diversification. The absence of the Trw system, which facilitates host switching in lineage 4 (L4), may constrain ecological breadth in L3, thought to be undergoing a parallel adaptive radiation with L4. The discovery of B. bennetti sp. nov. underscores the importance of combining genomic, ecological and evolutionary evidence when delimiting species boundaries in Bartonella and raises new hypotheses about the role of Hfr-mediated recombination in the evolutionary dynamics of host-adapted pathogens. The type strain of B. bennetti sp. nov. is C271T (CSUR B1113T, NCTC 15117T).

Item Type:	Article
Uncontrolled Keywords:	Bartonella evolution; comparative genomics; plasmid; virulence; Animals; Bartonella; Bartonella Infections; DNA, Bacterial; RNA, Ribosomal, 16S; Bacterial Typing Techniques; Sequence Analysis, DNA; Genomics; Phylogeny; Genome, Bacterial; Arvicolinae; Type IV Secretion Systems; Bartonella evolution; comparative genomics; plasmid; virulence; Animals; Bartonella; Phylogeny; DNA, Bacterial; Genome, Bacterial; Genomics; Sequence Analysis, DNA; RNA, Ribosomal, 16S; Arvicolinae; Bacterial Typing Techniques; Type IV Secretion Systems; Bartonella Infections; 3107 Microbiology; 31 Biological Sciences; 3104 Evolutionary Biology; 3105 Genetics; Biotechnology; Genetics; Animals; Bartonella; Phylogeny; DNA, Bacterial; Genome, Bacterial; Genomics; Sequence Analysis, DNA; RNA, Ribosomal, 16S; Arvicolinae; Bacterial Typing Techniques; Type IV Secretion Systems; Bartonella Infections; 0603 Evolutionary Biology; 0605 Microbiology; 1108 Medical Microbiology; Microbiology; 3104 Evolutionary biology; 3107 Microbiology
Subjects:	Q Science > QL Zoology
Divisions:	Biological and Environmental Sciences (from Sep 19)
Publisher:	Microbiology Society
Date of acceptance:	13 February 2026
Date of first compliant Open Access:	23 July 2026
Date Deposited:	23 Jul 2026 13:07
Last Modified:	23 Jul 2026 13:07
DOI or ID number:	10.1099/ijsem.0.007095
URI:	https://researchonline.ljmu.ac.uk/id/eprint/29052

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