Bacteria acquire up to 90% of their genetic material from distantly related bacteria species, according to research from the University of Arizona, Tucson. The finding has important biomedical implications because such gene-swapping, or lateral gene transfer, is the way many pathogenic bacteria pick up antibiotic resistance or become virulent.
"To maintain effective treatments and develop new antibiotics, it's important to monitor the rates and patterns of lateral gene transfer," stresses Howard Ochman, professor of biochemistry and molecular biophysics.
The research also solves a longstanding evolutionary puzzle. Many scientists have argued that drawing traditional family trees does not make sense for bacteria because their genomes represent a mix of genetic material from their parental cells and from other species of bacteria. Ochman's work shows that bacterial lineages still can be traced by considering only the "traditional" forms of genetic inheritance. The widespread exchange of genes does not blur the line of descent since the acquired genes get lost from the genome at a later point or, if they do persist, the bacteria then transmit them to their offspring.
Being able to classify bacteria is crucial for medicine, Ochman adds. "If you go to the doctor with strop throat, he can be pretty certain that it's the result of an infection with a species of Streptococcus and can therefore prescribe an appropriate antibiotic. If you couldn't classify bacteria because they have genes from all over, doctors wouldn't be able to do this."
Lateral gene transfer, unique to the bacterial world, long has been recognized. Until now, though, scientists did not know which of a bacterium's genes came from lateral gene transfer and which had been inherited from its parent. Ochman's team focused on the best-studied group...