The age-old battle between bacteria and viruses

Viruses have been the arch enemies of bacteria since the beginning of time; every day bacteriophages, a type of virus, kill a third of all bacteria in the oceans. Such a virus invades the cells of a bacterium, injects its DNA or RNA and thereby tries to take control of the cell. If the hijacking is successful, the virus can use the cell as a factory to multiply itself. A strategy as simple as it is deadly.

Stan Brouns is engaged in fundamental research on this billion-year battle between bacteria and viruses, by studying the ways in which bacteria can defend themselves against viral infections. In particular, he is looking at the so-called CRISPR-Cas defence mechanisms that bacteria deploy to arm themselves against viruses. As a result of his research, we now know that bacteria have a smart, adaptive immune system that can remember and render invaders harmless, similar to the immune system in the human body, albeit according to completely different principles.

Broun’s research helped pave the way for the pioneering CRISPR-Cas9 technique, a type of molecular scissors that can cut a piece of DNA with unprecedented precision. It unleashed a revolution in genetics because of its wide range of (therapeutic) applications in medical and biotechnology laboratories. Many diseases are caused by gene mutations, and CRISPR may now soon be used to correct errors in DNA, for example. Recently, Brouns discovered another new molecular tool, namely a technique that can also cut the RNA of viruses and proteins to render them harmless. In addition, Brouns found that when cutting the virus in an infected cell is insufficiently effective, the cell quickly kills itself, preventing the virus from infecting surrounding cells.

As well as his CRISPR research, Brouns is leading an innovative study of bacteriophages as a possible alternative to antibiotics. Bacteriophages are viruses that are the natural enemies of bacteria and Brouns has established the Netherlands’ first open science biobank in which bacteriophages are made available for (clinical) research into alternative treatments for antibiotic-resistant infections.

In the coming years, Brouns hopes to expand the collection of bacteriophages further. He also wants to continue to unravel the many unknown defence mechanisms of bacteria. What the DNA of bacteria looks like is now known, but there are still major questions about the function of all those genes. The bacteriological immune system CRISPR proved crucial for the discovery of several molecular tools, and Brouns hopes to find more such microbiological goldmines in the future.