Figure 2.

Physical maps of 10 (I – X) fragments of B. hermsii linear plasmids that contain vsp genes (red arrows), vlp genes (blue arrows), and/or DHS elements (green arrows). Also shown are the locations of other open reading frames (ORF), which are indicated by gene names (e.g. femD and bdr) or by Borrelia burgdorferi gene names (e.g. BBG30) or paralogous family numbers (e.g. 50) (Casjens et al., 2000; Fraser et al., 1997). When an ORF had no discernible homology with a protein in the GenBank database, it was designated a hypothetical protein (HP). The arrowheads indicate either the direction of transcription in the case of vsp and vlp genes and other ORFs or the orientation with respect to the expression site for the DHS elements. The start and stop positions for each open reading frame or sequence element are given in Table S1 of supplementary materials. The vsp and vlp genes are further distinguished by the number of the serotype they specify (e.g. vsp6) and, in the case of vlp genes, by appending their membership in vlp sub-families α, β, γ, and δ. Pseudo genes are indicated by Ψ, and truncated or otherwise incomplete vsp or vlp sequences were not assigned a serotype number. The 12 different genotypes of the near-identical DHS elements are indicated by a letter (a – l) subscript (see Figure 5). Some fragments were identified with linear plasmids of known sizes: lp28-1, lp28-2, lp28-3, lp28-4, and lp32-1. The expression site in this example of serotype 7 is adjacent the right telomere of plasmid lp28-1; the expression site promoter is indicated by the raised arrow. Serotypes 7 and 21 are exceptional in having a silent vsp or vlp downstream of the active vlp at the expression site (Kitten and Barbour, 1990); in other serotypes only a single vsp or vlp gene is between the promoter and the sub-telomeric DHS (Restrepo et al., 1992).