Figure 1.

(A) A summary of Brucella LPS structure showing the sugar backbone of O-PS and core plus lipid A. Glu, glucose; Gln, glucosamine; Ma, mannose; Pe, N-formylperosamine; Qui, quinovosamine (based on Iriarte et al. (2004) and Gil-Ramírez et al. (2014). (B) Evolutionary scenario proposed for the O-polysaccharide in Brucella. The wbo locus was probably acquired by a single horizontal transfer event involving the unstable element GI-2 and its cognate integrase. In contrast, the wbk locus might evolve from a primary integration, followed by the addition of the wbkA gene by transposition. Thus, the wbkA region could serve as bait for transposition of related elements (shaded triangles). Black bars indicate direct repeats and a tRNA gene in wbo and wbk regions, respectively.