Alien genes in bacteria

Evidence for lateral gene transfer (LGT) contradicted earlier theories that bacteria evolve clonally, with daughters only inheriting genetic material from mothers. LGT is extensive and has played a major role in microbial evolution, and indeed genes may be transferred from phylogenetically quite distantly related organisms, making the construction of a meaningful phylogenetic tree difficult. In the August 8 Science, Vincent Daubin and colleagues of the University of Arizona argue, however, that too much weight is given to LGT in the phylogenetic analysis of bacteria, and by using a more conservative approach than the usual "reciprocal best hit" method to detect orthologous genes, they found that those available for phylogenetic reconstruction are consistent with a single tree (Science, 301:829-832, August 8, 2003).

Daubin et al. analyzed quartets of related sequenced genomes whose phylogenetic relationship is known based upon small subunit ribosomal RNA sequence. They inferred the number of genes...