A study of a helical movement of bacteria caught our attention. If the driving force in the tail of this bacterium is strong enough to cause the flow stress fluid in front of it to deform, it can move forward.
We all feel like we are walking in the mud from time to time, but for some creatures this is just the case. Many bacteria move in liquids that first act as solids but then flow when stretched by the action of the microorganism. Hadi Mohammadigoushki of Florida State University and colleagues identified two key thresholds a swimmer must cross to propel himself through these productively stressful liquids, in an experiment simulating a spiraling bacterium floating in mucus.
The team created a 3D-printed microbe model in the shape of a corkscrew, placed it in a high-viscosity polymer gel, and used a magnetic field to make it spin. Using particle tracking and imaging techniques, the scientists then measured the swimmer's speed and imaged the flow field surrounding it. Their research showed that in order for the swimmer to turn, the fluid must first overcome the yield stress.
Flow Voltage of Fluid
The flow stress of the fluid must then be low enough to cause a significant amount of fluid to move around the swimmer. Both situations result in movement only if the swimmer's tail thrust is strong enough to deform the surrounding fluid; If not, it stays still.
Movement speed is determined by the slope of the swimmer's corkscrew tail after movement begins.
This information could help predict how earthworms improve soil aeration, how fruit-eating parasites can infect crops, and how Helicobacter pylori corkscrews and ulcerates the gastrointestinal mucosa. The experimental method can also enable a more in-depth study of biological, medical, and agricultural issues related to material design and organismal mobility that were previously only solvable theoretically.
Source: physics.aps.org/articles/v16/s35
Günceleme: 17/03/2023 14:07