The tuf gene of eubacteria, encoding the EF-tu elongation factor, was duplicated early in the evolution of the taxon. Phylogenetic and genomic location analysis of 20 complete eubacterial genomes suggests that this ancient duplication has been differentially lost and maintained in eubacteria. (C) 2001 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.