A Phylogenetic Analysis of Borrelia Burgdorferi Sensu Lato Based on Sequence Information from the hbb Gene, Coding for A Histone-Like Protein

This study evaluates the phylogenetic utility of the hbb gene, which encodes a histone-like DNA-binding protein, for classifying Borrelia burgdorferi sensu lato strains that cause Lyme disease. Researchers sequenced the 327-bp hbb gene from 39 Borrelia strains, including 37 B. burgdorferi sensu lato isolates, plus B. turicatae and B. parkeri. Analysis revealed 81 nucleotide substitutions resulting in only 25 amino acid changes, with most variation in wobble positions. The phylogenetic tree generated from hbb sequences largely agreed with classifications from multilocus enzyme electrophoresis (MLEE) and DNA-DNA hybridization. The study confirmed the subdivision of B. burgdorferi sensu lato into five species (B. burgdorferi sensu stricto, B. garinii, B. afzelii, B. japonica, and "B. andersonii") and at least four additional genomic groups. The hbb gene proved more conserved than osp genes used in previous studies, with greater than 93% amino acid identity among B. burgdorferi sensu lato strains. The histone-like protein signature region was highly conserved at the amino acid level despite nucleotide variation, supporting the use of hbb for genus-level phylogenetic analysis.

Key findings

• The hbb gene (327 bp) proved suitable for phylogenetic inference in Borrelia, showing greater conservation (>93% identity) than previously studied genes like ospA, ospB, and ospC
• Analysis of 39 Borrelia strains confirmed subdivision of B. burgdorferi sensu lato into five recognized species and at least four additional genomic groups
• The histone-like protein signature region was highly conserved at the amino acid level (3 substitutions in 21 residues) despite higher nucleotide variation (14 substitutions in 63 nucleotides)
• hbb sequence-based phylogenetic tree showed strong agreement with classifications derived from MLEE and DNA-DNA hybridization methods
• The study enabled development of a sensitive nested PCR assay for detecting and phylogenetically characterizing diverse Borrelia strains without cultivation