Together, our data indicate that BoaA is an adhesin common to B. mallei and B. pseudomallei and mediates adherence to host cells relevant to pathogenesis by the organisms. These findings are consistent with the recent inclusion of BoaA (i.e. B. mallei ATCC23344 and B. pseudomallei K96243 locus tag numbers BMAA0649 and BPSS0796, respectively) in the virulome of B. mallei and B. pseudomallei, which consists of
a set of 650 putative virulence Anlotinib cell line genes that are shared by B. pseudomallei and B. mallei but are not present in five closely-related non-pathogenic Burkholderia species . Comparative genomic analyses revealed that several B. pseudomallei isolates possess a second Oca-like gene product highly similar to BoaA, which we termed BoaB. The C-terminus of BoaB is strikingly similar to that of BoaA (Fig 2) and the predicted passenger domains of the molecules contain numerous matching
serine-rich SLST motifs (Fig selleck screening library 1). The proteins are also functionally related as they mediate adherence to the same types of host cells (Fig 3D and 5). Therefore, it is tempting to speculate that boaA and boaB are the result of gene duplication. This hypothesis would be consistent with the genomic organization of the genes. In B. pseudomallei strains K96243, 1710b, 1655, 576 and MSHR346, the boaB gene is located on chromosome 1 while boaA is on chromosome 2. Moreover, the boaB gene in all these isolates is preceded by two ORFs specifying an invertase and a transposase. These genes may be the remnants of mobile genetic elements possibly Etofibrate involved in gene duplication. Database searches also revealed that B. mallei isolates do not possess a boaB gene, which was likely lost during evolution of the organism into a host-adapted pathogen. Interestingly, the closely-related bacterium Burkholderia thailandensis has been reported by others to bind poorly to epithelial cells . This organism exhibits high genomic similarities to B. pseudomallei and B. mallei and, like B. pseudomallei, is a natural inhabitant of the tropical soil environment. However, B. thailandensis is not considered pathogenic to humans or higher animals [84–87]. This difference in virulence can be attributed
to the fact that B. thailandensis does not produce a capsule  and lacks the 650 genes comprising the aforementioned virulome of B. mallei and B. pseudomallei. Analysis of the published genome of the B. thailandensis strain E264  indicated that it contains neither the boaA nor the boaB gene. B. pseudomallei DD503 and B. mallei ATCC23344 do not produce detectable amounts of the BoaA and BoaB proteins under the conditions tested. These results are consistent with qRT-PCR experiments demonstrating that the organisms express very low levels of the boa genes relative to the Burkholderia recA control (Fig 4). Similar observations were made by Druar and colleagues while studying expression of the Burkholderia Type 3 Secretion System-3 (T3SS-3) proteins BipB and BipD .