Do genealogical patterns in purple photosynthetic bacteria reflect interspecific gene transfer?

Abstract

It is generally thought that interspecific (lateral) transfer of genes is so extensive among bacteria that it is difficult, and perhaps impossible, to determine their phylogenetic relationships. Ambler and coworkers¹ reflect this in their suggestion that the relationships seen among cytochrome c sequences of the Rhodospirillaceae are merely the result of a haphazard lateral transfer of the particular gene, and give no indication of the true bacterial phylogenies. However, if comparative analysis of several unrelated macromolecules yields essentially the same phylogenetic tree, then that pattern is extremely unlikely to reflect the lateral transfer of genes². We have also determined 16S ribosomal RNA catalogues³ for many of the Rhodospirillaceae investigated by Ambler et al. and here we use these two sets of data to compare molecular phylogenies for these bacteria.