Biologists have observed an incredible microbial arms race, as bacteria fight to contain their killer viruses.

The rapid evolutionary back-and-forth between bacteria and the killer viruses they contain is the subject of a sophisticated genetic study of micro-organisms.

University of New South Wales researchers studied the evolution of Pseudomonas aeruginosa - bacteria that can cause chronic, often lethal lung infections in people with cystic fibrosis.

By sequencing the DNA of entire bacterial populations as they evolved in the laboratory, the team was able to identify the genetic mutations which allow rapid evolution.

“We uncovered an interesting arms race between the bacteria and the viruses,” says Dr Kerensa McElroy.

“We found the viruses are evolving unusually rapidly. And the bacteria defend themselves against the viruses by changing their surface structure, so the viruses cannot reinfect them.”

The research is important for understanding how bacteria evolve, to create better tools for protecting humans in future.

“Most antibiotics are failing us quite miserably, which has a lot to do with the rapid evolution that bacteria can undergo. It is vital to understand how they evolve, and the different pathways they can take, depending on the environment they live in,” says Associate Professor Torsten Thomas.

The study is published in the journal Proceedings of the National Academy of Sciences.