Figure 2.

Phylogenies of the key cas genes and organization of cas operons. (a) Phylogenetic tree for COG1518 proteins (b) Phylogenetic tree for COG1203 proteins (predicted helicase) from the CASS versions lacking COG1518 (c) Phylogenetic tree for the predicted CASS polymerase (COG1353). Prokaryotic lineages are color-coded: orange, archaea; blue, Proteobacteria; green, low-GC Gram-positive bacteria; black, other bacteria. In the operon organizations cartoons, orthologous genes are color-coded and denoted by either the predicted function or the COG number. Exclamation points denote previously undetected RAMPs. The names of species that have a reverse transcriptase gene within one of the cas operons are underlined in red. In the left panel, the distinct versions of CASS are numbered, and in the right panel, these numbers are given at tree leaves to indicate the helicase cassette(s) that co-occurs with the given polymerase cassette.