| − | |<ref>Doolittle RF, Feng DF, Anderson KL, Alberro MR. 1990. A naturally occur ring horizontal gene transfer from a eukaryote to a prokaryote. J. Mol. Evol. 31:383—88</ref> <ref>Martin W, Brinkmann H, Savonna C, Cerff R. 1993. Evidence for a chimeric nature of nuclear genomes: eubacterial origin of eukaryotic glyceraldehyde-3- | + | |<ref>Doolittle RF, Feng DF, Anderson KL, Alberro MR. 1990. A naturally occur ring horizontal gene transfer from a eukaryote to a prokaryote. J. Mol. Evol. 31:383—88</ref><ref>Martin W, Brinkmann H, Savonna C, Cerff R. 1993. Evidence for a chimeric nature of nuclear genomes: eubacterial origin of eukaryotic glyceraldehyde-3- |