Grouping of RNA phages based on the template specificity of their RNA replicases.

We attempted to apply a new criterion, the template specificity of RNA replicases of Escherichia coli RNA phages, for the grouping of these phages. Based on the template specificity, it was shown that (a) Qbeta, VK, and ST belonged to one group (group III), and SP and FI to another group (group IV), and (b) some similarity existed between groups III and IV. Considering such template specificity in addition to previously reported properties of phage particles, we could separate RNA phages into four major groups (I-IV) with subgroups a, b, and c in group III, and subgroups a and b in group IV.