According to new research from The University of Arizona in Tucson, bacteria acquired up to 90 percent of their genetic material from distantly related bacteria species. The finding has important biomedical implications because lateral gene transfer is the way many pathogenic bacteria pick up antibiotic resistance or become more virulent.

“To maintain effective treatments and develop new antibiotics, it’s important to monitor the rates and patterns of lateral gene transfer,” said team member Howard Ochman, a UA professor of biochemistry and molecular biophysics and a member of UA’s BIO5 Institute.

In their study, the scientists focused on the best-studied group of bacteria, the Gamma-Proteobacteria. It includes many human pathogens, including Salmonella, Shigella, pathogenic E. coli, and Pseudomonas.
Being able to classify bacteria is crucial for medicine, Ochman said:

“If you go to the doctor with strep 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.”

Genes are most commonly transmitted by bacteriophages – viruses that specifically hijack bacteria cells. Phages inject their own genetic material into the host bacteria cell, forcing it to produce new phages. Genes from the bacterial genome can then be incorporated into the newly made phages, creating newly modified genetic loads, which are then injected into other bacteria.
The research report is published in the current issue of PLoS Biology, available on