Long-Read Sequencing Reveals Genetic Adaptation of Bartonella Adhesin A Among Different Bartonella henselae Isolates

Abstract

Bartonella henselae is the causative agent of cat scratch disease and other clinical entities such as endocarditis and bacillary angiomatosis. The life cycle of this pathogen, with alternating host conditions, drives evolutionary and host-specific adaptations. Human, feline, and laboratory adapted B. henselae isolates often display genomic and phenotypic differences that are related to the expression of outer membrane proteins, for example the Bartonella adhesin A (BadA). This modularly-structured trimeric autotransporter adhesin is a major virulence factor of B. henselae and is crucial for the initial binding to the host via the extracellular matrix proteins fibronectin and collagen. By using next-generation long-read sequencing we demonstrate a conserved genome among eight B. henselae isolates and identify a variable genomic badA island with a diversified and highly repetitive badA gene flanked by badA pseudogenes. Two of the eight tested B. henselae strains lack BadA expression because of frameshift mutations. We suggest that active recombination mechanisms, possibly via phase variation (i.e., slipped-strand mispairing and site-specific recombination) within the repetitive badA island facilitate reshuffling of homologous domain arrays. The resulting variations among the different BadA proteins might contribute to host immune evasion and enhance long-term and efficient colonisation in the differing host environments. Considering the role of BadA as a key virulence factor, it remains important to check consistently and regularly for BadA surface expression during experimental infection procedures.

Adhesion of Bartonella henselae to Fibronectin Is Mediated via Repetitive Motifs Present in the Stalk of Bartonella Adhesin A

“…Scale bar: 250 aa. (B) The variety in molecular weight (MW) of all BadA mutant proteins is demonstrated via Western blotting using anti-BadA IgG antibodies ( 17 ). B. henselae strains HN2S27 and S30 display the largest (predicted as 343 kDa) and smallest (92 kDa) truncated BadA, respectively.…”

“…Consequently, strains S28 and S29 were designed in silico , synthesized according to the badA sequence (GenBank MK993576.1 ) of B. henselae Marseille ( 17 ), and cloned into vector pBBR1MCS-5 ( Table 2 ). Finally, B. henselae ΔBadA-T was transformed with the resulting plasmids via electroporation.…”

“…The modularly structured passenger domain of BadA includes a head domain and an exceptionally long neck/stalk region showing high variability among different B. henselae strains ( 17 , 18 ). Using state-of-the-art long-read sequencing technologies, we demonstrated recently that B. henselae Marseille contains a badA gene of 11,922 bp with a neck/stalk region that contains 30 repetitive domains ( 17 ). Neck/stalk domains share specific sequence motifs with characteristic conformations, annotated by the “domain dictionary” approach of the daTAA (domain annotation of TAAs) server ( 19 , 20 ).…”

The C‐terminal head domain of Burkholderia pseudomalleiBpaC has a striking hydrophilic core with an extensive solvent network

“…Using the domain annotations and our predicted homology models, the overall length of BpaC is about 55 nm including the anchor domain. BpaC (1152 residues) is thus at the lower medium‐sized end of the TAA spectrum compared to YadA (422 residues, ~20 nm; Hoiczyk et al, 2000) and BadA (3973 residues; Thibau et al, 2022); ~240 nm; Müller et al, 2011).…”

“…the anchor domain. BpaC (1152 residues) is thus at the lower medium-sized end of the TAA spectrum compared to YadA (422 residues, ~20 nm;Hoiczyk et al, 2000) and BadA (3973 residues;Thibau et al, 2022); ~240 nm;Müller et al, 2011).…”