Since the time of Darwin, the evolutionary relationships between organisms have been represented as a tree, with the common ancestors at the base of the trunk and the most recently evolved species at the tips of the branches. Microbiologists have argued for a long time that this representation doesn't really hold true for microbes, which often exchange genes among different species. Their claim has been that the evolution of these organisms is better represented by a net. Unfortunately, no-one knew exactly where to draw the horizontal lines in this net.
Victor Kunin, previously a PhD student in Christos Ouzounis's group, and their colleagues have now constructed a map of microbial evolution, going back billions of years to the last universal common ancestor, that includes these horizontal lines. "Reassuringly, evolutionary trees constructed by many independent methods and different research groups are remarkably consistent with each other, projecting the same story. We used these trees as the scaffold of the net, on which we looked for the evidence of horizontally transferred genes," explains Victor.
To get a grip on horizontal gene transfer, they used a method called GeneTrace, previously developed by Victor and Christos. GeneTrace infers horizontal transfer from the patchy presence of a gene family in distantly related organisms. The data generated by GeneTrace allowed them to draw 'vines', repres
Contact: Trista Dawson
European Molecular Biology Laboratory