Bacteria are an indiscriminate lot. While most organisms tend to pass their genes on to the next generation of their own species, bacteria often exchange genetic material with totally unrelated species – a process called lateral gene transfer.
That is why skeptics doubted that researchers could ever hope to work out the evolutionary history of bacteria. But now, thanks to the availability of sequenced genomes for groups of related bacteria, and a new analytical approach, researchers at the University of Arizona demonstrate that constructing a bacterial family tree is indeed possible.
Nancy Moran, Emmanuelle Lerat, and Vincent Daubin propose an approach that begins by scouring genomes for a set of genes that serve as reliable indicators of bacterial evolution. This method has important implications for biologists studying the evolutionary history of organisms by establishing a foundation for charting the evolutionary events, such as lateral gene transfer, that shape the structure and substance of genomes.
Bacteria promise to reveal a wealth of information about genomic evolution, because so many clusters of related bacterial genomes have been sequenced--allowing for broad comparative analysis among species--and because their genomes are small and compact.
In this study, the researchers chose the ancient bacterial group called gamma Proteobacteria, an ecologically diverse group (including Escherichia coli and Salmonella species) with the most documented cases of lateral gene transfer and the highest number of species with sequenced genomes.
The results support the ability of their method to reconstruct the important evolutionary events affecting genomes. Their approach promises to elucidate not only the evolution of bacterial genomes but also the diversification of bacterial species – events that have occurred over the course of about a billion years of evolution.
Lerat E. Daubin V, Moran NA (2003): From Gene Trees to Organismal Phylogeny in Prokaryotes: The Case of the g-Proteobacteria. DOI: 10.1371/journal.pbio.0000019. Download article PDF at:http://www.plos.org/downloads/moran.pdf.
The article is published online as a sneak preview to PLoS Biology, the first open-access journal from the Public Library of Science (PLoS). The article will be part of the inaugural issue of the new journal, which will appear online and in print in October 2003. PLoS is a non-profit organization of scientists and physicians committed to making the world's scientific and medical literature a freely available public resource (http://www.plos.org).
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