Distribution and content of vir gene clusters in eight diverse A. phagocytophilum strains. Top panel. Schematic representation of all vir loci (colored arrows) showing the three conserved gene cluster islands (see text). VirB-7, virB8-2 and virB9-2 are not part of vir gene clusters, but their location relative to surrounding genes is also highly conserved among strains. A small cluster comprising truncated (t) virB6 and virB4 gene fragments is present in all strains, but the Norwegian lamb strains have one additional virB4-t. Bottom panel. Magnification of the virB2 gene cluster. Numbering of paralogs 1–8 is based on the original ApHZ annotated genome (GenBank CP000235). Artificial gaps (stippled lines) were introduced to allow alignment of the more spatially conserved paralogs B2-1, 2–2 and 2–3 at one end, and B2-7 and 2–8 at the other end of the cluster. With the exception of virB2-9, lacking in ApHZ, the number and arrangement (but not necessarily sequence) of virB2 genes is highly conserved in all but the US ruminant ApVar-1 and ApNorLamb-V1, which have several additional virB2 genes. In both strains a sub-cluster of 6 distinct genes was present. Due to the repetitive nature of sequences in this region, combined with the relatively short length of 454 reads (≤550 bp), their placement could not be confidently ascertained (highlighted by arrows and ‘?’). Maps are drawn to scale. Double lines designate interruption in sequences. Genes belonging to the same grouping have the same color. oriC; origin of replication.
Al-Khedery et al. BMC Genomics 2012 13:678 doi:10.1186/1471-2164-13-678