RecA superfamily clusters.

A Lek protein clustering method was applied to all RecA superfamily members retrieved from the NRAA database, microbial genomes, and the GOS data set. The 23 clusters containing more than two sequences are listed. Clusters that contain only sequences from the GOS data set are noted as “GOS only.” When a cluster can be mapped to a RecA subfamily identified by Lin et al.[53], the family designation from that paper is shown in column 3.*These clusters of RecA fragments from the GOS data set were not included in the phylogenetic tree (Figure 1).**Although cluster 9 contained only GOS sequences at the time of the initial analysis, it was subsequently found to include marine archaeal homologs from more recent genome sequencing projects.