EVOLUTION OF THE RECA GENE AND THE MOLECULAR PHYLOGENY OF BACTERIA

The DNA sequences of the recA gene from 25 strains of bacteria are kno wn. The evolution of these recA gene sequences, and of the derived Rec A protein sequences, is examined, with special reference to the effect of variations in genomic G + C content. From the aligned RecA protein sequences, phylogenetic trees have been drawn using both distance mat rix and maximum parsimony methods. There is a broad concordance betwee n these trees and those derived from other data (largely 16S ribosomal RNA sequences). There is a fair degree of certainty in the relationsh ips among the ''Purple'' or Proteobacteria, but the branching pattern between higher taxa within the eubacteria cannot be reliably resolved with these data.