Phylogenetic tree of bacterial RFs. A. A consensus tree of bacterial RF genes. The tree was constructed with MEGA3 program  using neighbor-joining method using a set of nonredundant protein sequences and Dayhof substitution matrix, gaps were deleted during pairwise distance estimations. Branches corresponding to RF1 genes are shown in green, RF2 are in blue and RFH are in red. B. Distribution of RFH sequences across the bacterial tree obtained from Ribosomal Database Project 2 . Bacteria in which RFH sequences were found in the present study are marked with red circles. Note that the absence of red circles does not necessarily indicate the absence of RFH sequences.