Summary auto-generated
This study evaluated the groEL gene (encoding the heat-shock chaperonin protein GroEL) as a phylogenetic tool for classifying Bartonella species, emerging bacterial pathogens. The researchers amplified and sequenced the groEL gene from ten Bartonella isolates, including multiple strains of B. henselae, and compared sequences with eight other known species using three phylogenetic methods: parsimony, neighbor-joining, and maximum-likelihood. While 16S rDNA sequence comparison failed to reliably resolve relationships within the genus, groEL sequences produced highly robust phylogenetic trees with four strongly supported clusters: B. henselae and B. quintana (human pathogens); rodent-associated species (B. elizabethae, B. tribocorum, B. grahamii, B. taylorii); three B. vinsonii subspecies; and B. birtlesii with 'B. weissi'. Several species did not reliably group with others. The groEL gene also effectively subtyped B. henselae isolates into three variants (Houston, Marseille, and Fizz), though B. quintana strains were too homogeneous for subtyping. The study demonstrates that groEL is more informative than previously studied markers for precise phylogenetic classification of Bartonella species at the species level.
Key findings
- The groEL heat-shock chaperonin gene provides superior phylogenetic resolution compared to 16S rDNA for Bartonella species classification, establishing four well-supported major clusters
- GroEL sequencing successfully subtypes B. henselae into three distinct variants, though this approach failed for the more homogeneous B. quintana species
- Phylogenetic analysis reveals B. henselae and B. quintana (human pathogens) form a distinct cluster separate from rodent-associated Bartonella species and B. vinsonii subspecies
- Multiple Bartonella species (B. bacilliformis, B. alsatica, 'B. washoensis', B. clarridgeiae, B. doshiae) lack statistically supported phylogenetic relationships with other known species, suggesting need for additional analysis
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Abstract
Bartonella is a bacterial genus classified in the alpha-Proteobacteria on the basis of 16S rDNA sequence comparison. The highly conserved heat-shock chaperonin protein, GroEL, has proved to be a valuable resolving tool to classify ten Bartonella species. The groEL gene was amplified and sequenced from ten Bartonella isolates: Bartonella alsatica, Bartonella vinsonii subsp. arupensis, Bartonella taylorii, Bartonella tribocorum, Bartonella birtlesii, Bartonella henselae Marseille (URLLY8), B. henselae (90-615), B. henselae (Fizz), B. henselae (CAL-1) and B. henselae (SA-2). Then, phylogenetic relationships were inferred between our isolates and eight other species and subspecies from the comparison of both 16S rDNA and groEL sequences using parsimony, neighbour-joining and maximum-likelihood methods. By using groEL sequences, the first reliable classification of most known Bartonella species and subspecies was established. Four strongly supported subgroups were distinguished: firstly, the two human pathogens B. henselae and Bartonella quintana; secondly, a cluster including four rodent isolates, Bartonella elizabethae, B. tribocorum, Bartonella grahamii and B. taylorii; thirdly, a cluster including the B. vinsonii subspecies (B. vinsonii subsp. vinsonii, arupensis and berkhoffii); and lastly, B. birtlesii and 'Bartonella weissi'. 'Bartonella washoensis', B. alsatica, Bartonella doshiae, Bartonella bacilliformis and Bartonella clarridgeiae did not reliably cluster with any other Bartonella species. In addition, the groEL gene was shown to be useful in subtyping six B. henselae isolates into three variants: Houston, Marseille and Fizz.