The graphene membrane reveals bacterial sounds.

Have you ever wondered if microbes generate unique sounds? We would be able to tell whether bacteria are alive or not if we could listen to them. Those sounds would stop if bacteria were destroyed with an antibiotic, unless the bacteria were resistant to the drug. This is exactly what a team of TU Delft researchers led by Dr. Farbod Alijani has just accomplished: they collected low-level noise from a single bacterium using graphene. Their findings have now been published in Nature Nanotechnology.

The sound of a single bacteria

Farbod Alijani’s team was initially investigating the principles of graphene physics, but they began to question what would happen if this very delicate material came into contact with a single biological thing. Graphene is a type of carbon that consists of a single layer of atoms and is also known as the “wonder substance,” Alijani explains. “It’s quite strong, with good electrical and mechanical qualities, but it’s also extremely sensitive to external stimuli.”

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

Dr. Farbod Alijani

The researchers began working along with Cees Dekker’s nanobiology group and Peter Steeneken’s nanomechanics group. The team conducted their first tests using E. coli bacteria with the help of Ph.D. student Irek Roslon and postdoc Dr. Aleksandre Japaridze. Cees Dekker (Cees Dekker): “What we observed was eye-opening. When a single bacterium attaches to the surface of a graphene drum, it produces random oscillations with amplitudes as low as a few nanometers, which we were able to detect. We were able to hear the sound of a single bacterium.

Using a microorganism to punch a graphene drum

The incredibly tiny oscillations are caused by bacterial biological activities, with the flagella playing a major role (tails on the cell surface that propel bacteria). To put these flagellar hits on graphene into perspective, consider that they are at least 10 billion times smaller than a boxer’s punch when it reaches a punch bag. These nanoscale beats, however, may be transformed into music recordings and listened to—how fantastic is that? Alijani explains.

Graphene for rapid antibiotic resistance detection

This study has far-reaching consequences for detecting antibiotic resistance. The results of the experiment were unequivocal: if the bacteria were resistant to the antibiotic, the oscillations just remained at the same level. When the germs were receptive to the medicine, the vibrations diminished until one or two hours later, when they vanished completely. The effect can be identified with a single cell due to the high sensitivity of graphene drums.

According to Farbod Alijani, “In the future, we hope to improve and test our single-cell graphene antibiotic sensitivity platform against a wide range of pathogenic samples.” As a result, it will eventually be able to be utilized as a useful diagnostic toolset for the rapid detection of antibiotic resistance in clinical practice.

“This would be a vital weapon in the fight against antibiotic resistance, an ever-increasing threat to human health around the world,” says Peter Steeneken.

“Probing nanomotion of single bacteria with graphene drums,” the study’s title says.

I.E. Roslon, A. Japaridze, P.G. Steeneken, C. Dekker, and F. Alijani, “Probing nanomotion of a single bacterium with graphene drums,” Nature Nanotechnology, April 18, 2022.

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