Universiteit Leiden

nl en

Bacteria without cell wall gobble up DNA from environment

A bacterium hiding from the immune system and picking up bits of DNA from its environment. The result: gaining new traits, such as better protection against antibiotics. Fortunately, we have not found such a damning scenario yet. However, PhD student Renée Kapteijn did find the first clues, which she publishes today in Nature Communications.

Renée Kapteijn at the microscope.

The bacteria Kapteijn studies, streptomycetes, can live temporarily without a cell wall. ‘This sturdy barrier is normally a defense against external dangers, but then only the thin cell membrane remains. That's called the L-form,’ she explains. ‘The absence of the cell wall gives bacteria opportunities, such as hiding from viruses that target them.’

The safety of new biotech inventions

Kapteijn is part of the labs of Gilles van Wezel and Dennis Claessen (Institute of Biology Leiden). ‘I started in 2018 as a PhD student on the TargetBio-project. We investigate the safety of all kinds of new biotechnogical inventions. One possible example is DNA that ends up in the environment unintentionally. In my paper, I show that bacteria without a cell wall can get a use out of that.’

In the dark vesicle the magenta DNA is taken up by the bacteria.

Internal bubble to trap DNA

Kapteijn discovered that L-form bacteria are able to take up DNA spontaneously. To do so, the L-forms use a method previously unseen by bacteria: endocytosis. The cell membrane bends further and further inwards, like a reverse bubble. Once the membrane completely surrounds the liquid, it enters the cell as a vesicle. ‘We saw that in this way, magenta fluorescent labelled DNA got taken up in the bacterial cells.’

We already knew this is possible in multicellular organisms, such as plant and animal cells. But now we are showing this for the first time in bacteria. Very cool to see under the microscope,’ says Kapteijn enthusiastically.

Testing with large nanoparticles

It also gave the opportunity for further experiments. For example, by testing the maximal size that the L-forms could absorb. For this, she collaborated with Alexander Kros' group from the Leiden Institute of Chemistry (LIC), which made nanoparticles of 150 nano-meters. These too were taken up by the L-forms, indicating that uptake is not specific to DNA. They seem to take up everything present in the fluid around the cell. ‘However, we did see that it costs the bacteria energy, so it does not appear to be an endless method of taking up environmental substances,’ Kapteijn believes.

With the elektron microscope, several visicles become visible.

Symbiosis between biology and chemistry

Surely, Kapteijn also found the period leading up to the publication quite exciting. ‘I spent most of my four PhD years working towards this. Writing a good publication is also challenging. But I am proud that we managed to do this great research together. And that we also looked at the project from so many sides.' Alexander Kros also agrees. 'This joint project is an excellent example of a symbiosis between biology and chemistry. That now comes together in this fine article. It also certainly provides opportunities to tackle even more challenging problems in the future, combining the best of both worlds.'

Read the publication

Kapteijn, R., Shitut, S., Aschmann, D. et al. Endocytosis-like DNA uptake by cell wall-deficient bacteria. Nat Commun 13, 5524 (2022). https://doi.org/10.1038/s41467-022-33054-w

This website uses cookies.  More information.