Breaking down the microbiology world one bite at a time
Micromachines: Using bacteria to create an oscillator
If you have ever read or watched science fiction, you might have come across the idea of biological machines, perhaps nanobots, or organic-matter powered computers, or some other idea that you probably assumed was completely ridiculous because, let’s face it, that is a ways away for us. Or is it?
There are, in fact, a few examples of similar ideas happening right now. One of them is the motile active matter. Active matter defines matter whose components consume energy to do something; such as any living being most of the time, or a moving machine. Motile active matter is simply active matter that can use that energy to move. Understanding and predicting this movement is crucial for moving robots, swimming micromachines, and many others.
Bacteria as motile active matter
Bacteria move. But how and why is a complicated question. Can we predict it? The scientists behind this article decided to experiment on it. For this they used the very common bacteria Escherichia coli. They placed a singular bacterial cell in a tiny well. The bacterium started swimming. Then, they changed the shape and size of the well. The bacterium within it started moving…differently.
Overall, the bacteria had a tendency to move around the circular space, close to the walls. But if the cavities were too big, then they started swimming elsewhere. Engineering the cavity size allowed the scientists to determine the motion of the bacteria. With small enough cavities (7 µm), the bacteria simply moved around the space, taking the same time to do a whole loop, thereby creating an oscillator.
Oscillators are electronic components that provide a periodic signal. Tracking the bacteria in the cavities resulted in an oscillator and provided a signal when the bacteria reached a certain point. And modulating the cavity characteristics, such as diameter, made it so the bacteria would take more or less time to do a loop, thus changing the signal frequency.
Synchronization of bacteria
As this was extremely interesting, the scientists then wondered if bacteria influenced each other’s movement. They made two cavities, each with their own bacterium, and connected them with a small channel. To their surprise, the bacteria moved in rhythm, synchronizing their movement for a while, then moving at different rates for another bit of time. This pattern repeated over and over.
The researchers investigated more about their synchronization, and realized that it was mediated by the properties of the channel. With no channel, the bacteria did not synchronize their movement. The longer and wider the channel, the more they synchronized. It was unclear if this pattern emerged from some communication between the bacteria, or simply the sensing of each other’s movement.
Mathematical modeling of synchronization
The scientists tried to see if they could fit the synchronization pattern of the oscillating bacteria to a mathematical equation or model. Amazingly, they discovered that the simplest synchronization model, Adler’s equation, describes the pattern that they saw in the bacteria. This means that they could predict the results of experiments with reasonable accuracy. Having a system that obeys a mathematical model is incredibly important for reliability, if it is to be used in more complex processes.
Reality meets science fiction
Controlling the cavities’ size and parameters allows modulation of the oscillatory properties of the bacteria. And controlling the length and width of the channel joining the two cavities allows control of the synchronization patterns. The scientists themselves looked forward to testing other hypotheses, and they stated that this paves the way for more complex systems, where bacteria are used as oscillators, or more complex networks of synchronized bacterial oscillators.
Machines powered or controlled by biological matter are not as far as we may have imagined. Microfabrication cannot produce the complexity of living organisms yet, and harnessing the power of living matter might prove crucial for future micromachines. Replicating electrical circuits and components using living matter is simply the first small step in a long road, but as such, perhaps the most important step.
Link to the original post: Japaridze, A., Struijk, V., Swamy, K., Rosłoń, I., Shoshani, O., Dekker, C., & Alijani, F. (2024). Synchronization of E. coli Bacteria Moving in Coupled Microwells. Small, 2407832.DOI: 10.1002/smll.202407832
Featured image: Created by author using Canva’s Dream Lab
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