Identification and functional genomic analyses of Bartonella isolates from honey bees, and reassessment of the taxonomy of the genus Bartonella

Area of Science:

• Microbiology
• Genomics
• Taxonomy

Background:

• Bartonella species are known insect endosymbionts.
• Honey bee gut microbiota composition is crucial for bee health.
• Previous studies have identified Bartonella in honey bees, but taxonomic classification remains challenging.

Purpose of the Study:

• To identify and taxonomically classify Bartonella isolates from Belgian honey bee gut samples.
• To investigate the phylogenetic and functional divergence within Bartonella clades.
• To propose novel genera for reclassifying specific Bartonella groups.

Main Methods:

• Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for initial identification.
• Whole-genome sequencing and phylogenetic analyses (OrthoANIu, digital DNA-DNA hybridization).
• Functional annotation and comparative genomics.

Main Results:

• 90 Bartonella isolates were identified, including Bartonella apihabitans, Bartonella choladocola, and challenging B. apis-like isolates.
• Phylogenomic analyses did not support clear separation between B. apis and B. apis-like strains, leading to their combined classification.
• Two novel genera, Attibartonella gen. nov. and Ditibartonella gen. nov., were proposed for the Bartonella tamiae and honey bee-associated Bartonella clades, respectively.
• Ditibartonella species showed evolutionary adaptation to bee hosts and potential shared transmission routes.

Conclusions:

• The study proposes the reclassification of Bartonella tamiae into Attibartonella tamiae comb. nov. and honey bee-associated Bartonella into Ditibartonella apis comb. nov.
• Phylogenomic and functional analyses support the establishment of these new genera.
• Ditibartonella bacteria exhibit host-specific adaptations and likely share transmission routes within bee populations.