Zen philosophers may ponder the sound of a hand clapping, but researchers have recorded the sound of a bacterium drumming.
Additionally, this acoustic research may provide another tool in the fight against antibiotic resistance.
According to the World Health Organization fact sheet on the topic: “Antibiotic resistance is one of the greatest threats to global health, food security and development today.
“Bacteria, not humans or animals, become resistant to antibiotics. These bacteria can infect humans and animals, and the infections they cause are more difficult to treat than those caused by non-resistant bacteria.”
To determine if bacteria are becoming resistant to an antibiotic, researchers need to know if the drugs can efficiently kill bacteria.
By recording the sounds of a bacterium beating a microscopic drum, researchers at TU Delft in the Netherlands, led by Dr. Farbod Alijani, were able to efficiently check the health of the bacterium using sound. His work was published yesterday in the magazine Nature Nanotechnology.
So how can a bacterium play a drum?
The researchers were originally investigating the drum, which is a form of carbon called graphene, not the drummer.
“Graphene is a form of carbon that consists of a single layer of atoms and is also known as the wonder material,” says Alijani. “It’s very strong with good electrical and mechanical properties, and it’s also extremely sensitive to external forces.”
To test this sensitivity, the team decided to see what would happen if graphene encountered a single biological object…a single E. coli bacterium.
“What we saw was amazing!” Alijani says. “When a single bacterium sticks to the surface of a graphene drum, it generates random oscillations with amplitudes as low as a few nanometers that we were able to detect. We could hear the sound of a single bacterium.”
Most of the oscillations were being driven by E. coli flagella. Flagella are tail-like or hair-like structures on the cell surface that wiggle and spin, propelling the cell.
“To understand how small these flagellar beats are in graphene, it’s worth saying that they are at least 10 billion times smaller than a boxer’s punch when reaching for a punching bag,” says Alijani. “However, these nanoscale beats can be made into soundtracks and listened to, and what good is that?”
But how can bacteria that have picked up the pace be used to fight disease?
This research is still early days, but Alijani and his team are hopeful that it can be used to identify bacteria that have become resistant to antibiotics.
When resistant bacteria were exposed to antibiotics in the graphene drum, their oscillations continued at the same level: the rhythm did not stop.
But when the bacteria were susceptible to a drug, the rhythm died along with the bacteria. After exposure to antibiotics, these dying bacteria sang a song that was operatic in length, if not scale. The vibrations they created would slowly subside over the span of an hour or two until they finally ceased.
The wonder of this technology is that it can detect antibiotic resistance at the single-cell scale.
“Moving forward, we aim to optimize our single-cell graphene antibiotic sensitivity platform and validate it against a variety of pathogenic samples,” says Alijani. “So that it can eventually be used as an effective diagnostic toolkit for rapid detection of antibiotic resistance in clinical practice. “This would be an invaluable tool in the fight against antibiotic resistance, a growing threat to human health around the world.”