‘My PhD research is about the cell wall of bacteria. I see the bacterial cell wall as a kind of jacket: when a bacterium wears its jacket, it is warm and safe. But when she throws off her jacket, she is naked and fragile. The cell wall is therefore the protective layer of the bacteria against the outside world. Before my research, it was already known that bacteria can lose their cell wall, but that phages could play a role in this was new.
Phages are viruses that can infect and kill bacteria. Just as a human is infected by a virus, a bacterium is infected by a phage. I had only been doing my research for three months when I decided to throw some things together in the lab. I wanted to see what would happen if I added phages to bacteria.
‘Many researchers are interested in phage therapy because it could become an alternative to antibiotics in the future. The problem with antibiotics is that more and more bacteria are becoming resistant. In addition, antibiotics also kill the good bacteria in our body. The great advantage of phages is that they often only recognize one specific species of bacteria. As a result, they only kill the pathogenic bacteria and the risk of side effects is smaller.
‘Before I threw the phages at the bacteria, I looked at my bacteria under the microscope. They looked good: they had an elongated shape and were swimming. So I added the phages and went to sleep. The next day I looked again. Then all the bacteria were round and stood still. That meant they had taken off their jackets.
‘I immediately took a picture, ran to my professor and told him to come and have a look. We looked at my bacteria through the microscope: they had all lost their cell wall. We cheered in the lab.
‘After a lot of brainstorming sessions, we realized that our discovery could be very important for phage therapy, especially for its limitations. Because if bacteria lose their cell wall, they are no longer recognized by phages and therefore not killed. Once the phages are gone, the bacteria put on their jacket again and the patient still has an infection.
‘Still, I don’t think that all phage therapies can go in the trash. Bacteria can only take off their jacket in certain circumstances that occur, for example, in the blood and in the bladder. But in other places, such as on the skin, you could still use phage therapies, because the phages there are able to kill bacteria.
‘There are also ways to circumvent this defense mechanism of bacteria. For example, we discovered a number of phages that can still recognize bacteria without a cell wall. This is because some bacteria do not throw off their jacket completely: a piece of sleeve remains. This way the phages can still recognize and kill the bacteria.
‘My research will take another two years. We study bacteria that can survive a phage infection. We’re trying to figure out how to kill them anyway. I try everything and hope to be lucky again. After all, I had that last time too.’
Véronique Ongenae is a PhD student at Leiden University. She conducts research into bacteria that can lose their cell wall.