A unique defense: bacteria lose cell wall in the presence of virus

Bacteria live temporarily without their cell wall when dangerous viruses are around. Remarkable, because the cell wall is a strong barrier against threats. Still, the discovery has a logical explanation and could have a consequence for the fight against pathogenic bacteria, according to Véronique Ongenae, lead author of the publication in Open biology†

Bacteria can live without a cell wall a time in stressful circumstances, the group led by Dennis Claessen, professor at the Institute of Biology Leiden (IBL) discovered in 2018. “But the goal was not yet clear. My role is to find that advantage, as a PhD student in the research group,” says Ongenae. “That’s why I also work with Streptomyces, which are the bacteria which we found could live without their cell wall.”

An accidental find

Ongenae grew Streptomyces in a so-called hyperosmotic environment. It has a high concentration of glucose, which allows bacteria to lose their cell wall, instead of breaking down. Ongenae: “I experimented wildly to make the bacteria lose their cell wall, and wondered what would happen if I added bacteriophages to the Streptomyces. They are viruses that infect bacteria. And immediately all Streptomyces lose their cell walls. I could can’t believe my eyes. So I repeated the experiment over and over, but the result remained the same.”

With other known bacteria, such as Escherichia coli and Bacillus subtilis, Ongenae noted the same response to the presence of phages in a hyperosmotic environment. She suspects that bacteria lose their cell walls as soon as they become infected by the phage. “That’s something we’re looking at, but it looks like a defense mechanism,” notes Ongenae. “By losing their cell wall, bacteria become unrecognizable to the phage and remain under the radar.”

Danger to people

The interesting discovery also reveals potential complications in the treatment of infections. “Nowadays, phage therapies are increasingly used as a replacement for antibiotics, to rid the body of pathogenic bacteria. resistance to antibiotics increasingly common, phage therapy may be considered a new way to treat infections. But now it turns out that bacteria can hide from phages. And if our blood vessels and urine also form a hyperosmotic environment, bacteria can also live there without a cell wall. So if the phages leave the body after a few days, bacteria will regrow their cell walls and bring back the infection.”

That is why Ongenae is also conducting research into the effect on pathogenic bacteria, such as Pseudomonas aeruginosa and Acinetobacter baumannii. “Only then will we know if this is something to take into account.”