Contextual information graph, domain architectures, gene neighborhoods, cartoon and topology diagrams. A) Contextual information was derived from gene neighborhoods, domain architectures and functional associations (see methods used to obtain contextual information [Additional file 1]). Black arrows represent domain architectures with the arrow head pointing to the C-terminal domain. Red arrows represent gene neighborhoods, with the arrow head pointing from the 5' to 3' direction of the coding sequence. Blue edges represent physical associations and the green edge depicts domain insertion. Domain architectures of TV-Pol proteins are shown at the bottom. Gene neighborhoods (predicted operons) of TV-Pol proteins are shown to the right. Genes are represented as pointing from the 5' to the 3' end of the coding sequence. Below each gene-neighborhood cartoon is the representative TV-Pol gene name, it species abbreviation and gi. The "D5 Helicase" module includes both the core AAA+ ATPase domain and the unique D5N domain of these proteins. Likewise in the AEP module the PRICT1/2 domains are included. B) Cartoon representation of the Taq DNA polymerase (pdb: 1BGX) showing key structural units shared by TV-Pols and superfamily A polymerases. The HTH is shown in blue and the thumb domain in faded yellow. Active site and other key conserved residues are highlighted as ball and stick and labeled. C) Topology diagram of the core catalytic domain of these polymerases with key conserved features and residues. Cylinders represent helices and green arrows strands. D) Cartoon representation of various HTH domains in comparison with that seen in superfamily A DNA polymerases. Species abbreviations are in the legend to Fig. 2.