Bacterial soundtracks revealed by graphene membrane

A team of scientists at TU Delft has found a way to hear whether bacteria are still alive. If you don’t hear anything anymore, the bacteria are dead. The scientists led by Dr. Farbod Alijani have published their research in Nature Nanotechnology.

Farbod Alijani’s team was originally looking into the fundamentals of the mechanics of graphene, but at a certain point, they wondered what would happen if this extremely sensitive material comes into contact with a single biological object.

The sound of a single bacterium 

 “Graphene is a form of carbon consisting of a single layer of atoms and is also known as the wonder material,” says Alijani. “It’s very strong with nice electrical and mechanical properties, and it’s also extremely sensitive to external forces.”

The team of researchers initiated a collaboration with the nanobiology group of Cees Dekker and the nanomechanics group of Peter Steeneken. Together with PhD student Irek Roslon and postdoc Dr. Aleksandre Japaridze, the team ran their first experiments with E. coli bacteria. Cees Dekker: “What we saw was striking! When a single bacterium adheres to the surface of a graphene drum, it generates random oscillations with amplitudes as low as a few nanometers that we could detect. We could hear the sound of a single bacterium!”

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Punching a graphene drum with a bacterium

The extremely small oscillations are a result of the biological processes of the bacteria with the main contribution from their flagella (tails on the cell surface that propel bacteria). “To understand how tiny these flagellar beats on graphene are, it’s worth saying that they are at least 10 billion times smaller than a boxer’s punch when reaching a punching bag. Yet, these nanoscale beats can be converted to soundtracks and listened to – and how cool is that,” Alijani says.

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