What Do Bacteria Sound Like? Bacterial Soundtracks Revealed by Nanotechnology

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Bacterium on Graphene Drum

A graphene drum can reveal the sound of bacteria.

Have you ever wondered if bacteria make distinctive sounds? If we could listen to bacteria, we would be able to know whether they are alive or not. When bacteria are killed using an antibiotic, those sounds would stop – unless of course, the bacteria are resistant to the antibiotic. This is exactly what a team of researchers from TU Delft, led by dr. Farbod Alijani, has now managed to do: they captured low-level noise of a single bacterium using <span class="glossaryLink" aria-describedby="tt" data-cmtooltip="

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Graphene is an allotrope of carbon in the form of a single layer of atoms in a two-dimensional hexagonal lattice in which one atom forms each vertex. It is the basic structural element of other allotropes of carbon, including graphite, charcoal, carbon nanotubes, and fullerenes. In proportion to its thickness, it is about 100 times stronger than the strongest steel.

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Nature Nanotechnology.

The sound of a single bacterium

Farbod Alijani’s team at Delft University of Technology (TU Delft) was originally investigating the fundamentals of the physical mechanics of graphene, when a curious idea struck them. They wondered what would happen if this extremely sensitive material came into contact with a single biological object. “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.”

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This animation shows how a graphene drum can reveal the sound of bacteria. The sound stops when a bacterium is killed by an antibiotic. Credit: Irek Roslon – TU Delft

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Farbod Alijani’s 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 scientists ran their first experiments using 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!”

Punching a graphene drum with a bacterium

The extremely small oscillations are a result of the biological processes of the bacteria with 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 punch bag. Yet, these nanoscale beats can be converted to sound tracks and listened to — and how cool is that,” Alijani says.

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Bacterium on Graphene Drum

Artist’s impression of a graphene drum detecting nanomotion of a single bacterium. Credit: Irek Roslon, TU Delft

Graphene for fast detection of antibiotic resistance

This research has enormous implications for the detection of antibiotic resistance. The experimental results were unequivocal: If the bacteria were resistant to the antibiotic, the oscillations just continued at the same level. When the bacteria were susceptible to the drug, vibrations decreased until one or two hours later, but then they were completely gone. Thanks to the high sensitivity of graphene drums, the phenomenon can be detected using just a single cell.

Farbod Alijani: “For the future, we aim at optimizing our single-cell graphene antibiotic sensitivity platform and validate it against a variety of pathogenic samples. So that eventually it can be used as an effective diagnostic toolkit for fast detection of antibiotic resistance in clinical practice.” Peter Steeneken concludes: “This would be an invaluable tool in the fight against antibiotic resistance, an ever-increasing threat to human health around the world.”

Reference: “Probing nanomotion of single bacteria with graphene drums” by Irek E. Rosłoń, Aleksandre Japaridze, Peter G. Steeneken, Cees Dekker and Farbod Alijani, 18 April 2022, Nature Nanotechnology.
DOI: 10.1038/s41565-022-01111-6

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