Bacteria also make noises: research shows that they apparently can make a type of percussion music. To this end, scientists have developed tiny drums with graphene membranes that can register the vibrations of individual bacteria, making them audible. According to them, the concept could be beneficial in testing antimicrobials. Because drumming can be used to read exactly how a substance affects the microbes: tests show, for example, that the lethal effect of an antibiotic can be recognized by the cessation of head beating and flagella.
No matter how quietly we sneak, our movements generate vibration and thus noise. Even the very delicate movements of living things can still be recorded with modern instruments. For example, scientists have already registered the crackling, crunching and cracking caused by worms and the like in the ground. However, there are still much smaller organisms that move around and therefore at least theoretically cause vibration and thus noise. However, you might think that it is no longer possible to register fine microbial movements. But that’s exactly what the scientists led by Farbod Alijani from Delft University of Technology have now managed to do.
Scientists originally studied the basic mechanics of graphene. “It is a form of carbon consisting of a single layer of atoms and is also known as a wonder material. Because it is very durable, it has good electrical and mechanical properties and is extremely sensitive to external forces, ”explains Alijani. At one point, as part of their research, Alijani and his colleagues wondered what would happen if this extremely fragile material came into contact with a single biological object – and a very tiny one at that. Thus, scientists finally developed their graphene-bacterial drums.
Percussion music of a special kind
The ‘instrument’ membranes consist of ultra-thin double layers of graphene. They cover round indentations etched in silicon dioxide with a diameter of 8 micrometers and a depth of 285 nanometers. Many of these drums are stacked side by side on a silicon chip to ensure detailed test results. To record the movements of individual bacteria, one was attached to each of the graphene membranes. The entire system is in the nutrient medium. The researchers used the well-known gut bacterium Escherichia coli as the test microbe.
As reported by the scientists, they were actually able to detect the deflection of graphene membranes caused by the movements of bacteria. These vibrations were detected by laser interferometry. A single cell of Escherichia coli generates vibrations with an amplitude of up to 60 nanometers and exerts forces up to six nanonewtons on the environment. These effects could also be represented as sounds, which made it possible for scientists to hear the microbes. “What we saw was amazing! When a single bacterium sticks to the surface of the graphene drum, it produces vibrations that we were able to detect. It also allowed us to hear the sound of a single bacterium! ”Says co-author Cees Dekker of TU Delft.
The researchers explain that fine vibrations are the result of biological processes in bacteria, which are caused in particular by flagella movements. This has been illustrated by experiments with E. coli strains that have been genetically engineered to have different levels of locomotor activity depending on the number or activity of their flagella. “To understand just how small these graphene blows are, imagine that they are at least 10 billion times weaker than a boxer punch hitting the punching bag. Still, these nanoscale bits can be turned into audio tracks and listened to, ”says Alijani.
Potential for Antibiotic Research
Further experiments by the scientists then illustrated the potential of the research process. They administered antibiotics to “drummers” made of various strains of bacteria. It turned out that if a given bacterium was resistant to an antibiotic, the oscillations simply remained at the same level as before. On the other hand, if it was susceptible to the drug, the vibration would subside within an hour or two – until the beating finally dies with the death of the microorganism. The scientists emphasize that thanks to the high sensitivity of graphene drums, the action of antibiotics can be accurately understood at the level of a single cell.
“In the future, we want to further optimize our single-cell graphene susceptibility platform and test it against a variety of pathogens. Ultimately, the system could be used as an effective diagnostic tool for the rapid detection of antibiotic resistance in clinical practice, ‘Alijani hopes. His colleague Peter Steeneken concludes: “It would be an important tool in the fight against antimicrobial resistance, which is an increasing threat to human health worldwide.”
Video © Irek Roslon – HERE Delft
Source: Delft University of Technology, Article: Nature Nanotechnology, doi: 10.1038 / s41565-022-01111-6