New Publication in Science: Rapid evolutionary turnover of mobile genetic elements drives bacterial resistance to phages


Bacteria are constantly exposed to viral attacks. A research team led by Martin Polz, microbiologist at DOME, has studied how bacteria defend themselves against viral predators. The study – now published in Science – shows that bacteria have exchangeable genetic elements that are specifically designed for defense against viruses.

The question of how and how quickly bacteria develop resistance to viruses is of central importance for the development of phage-based therapies. Because of increasing antibiotic resistance, phages are considered a promising alternative to antibiotics in the treatment of bacterial infections. However, this requires a better understanding of the interaction between viruses and bacteria. A research project initiated by Martin Polz and his team at the Massachusetts Institute of Technology (MIT) in Cambridge (USA) – Polz moved from the MIT to CMESS about a year ago – elucidated this interaction studying how bacteria defend themselves against viruses. “Each bacterial cell has a surprisingly large set of defense genes that enable it to eliminate specific viruses,” explains the head of the research project. “Our study shows that these defense genes are exchanged very quickly between bacterial cells. This is possible because they are integrated into so-called mobile genetic elements that themselves control whether and when they transfer from one cell to another.” To date, the overall function of the mobile genome that typically comprises up to a third of bacterial genomes has remained poorly understood. The study now shows that it primarily serves one purpose: phage defense.

For three months, the researchers collected water samples on the New England coast every day to explore the interaction between Vibrio bacteria and co-occuring viruses. Over the 93 days of study, they observed how individual bacteria developed specific resistances via the exchange of mobile gene elements. This translates to bacteria being able to develop resistance to certain viruses within a few weeks to months in the wild. The findings not only provide knowledge on how microbial communities are functioning. They also point to challenges in combating bacteria with phages: “The rapid acquisition of resistance must be taken into account in developing phage therapies, precisely because mobile gene elements similar to those we studied are also responsible for the rapid development of antibiotic resistance,“ explains Martin Polz.

Photo © Kathryn Kauffman