Integration of evolutionarily distinct motility systems enables tunable cell propulsion
This study demonstrates that the predatory bacterium *Myxococcus xanthus* integrates its evolutionarily distinct gliding and twitching motility systems into a single, calcium-tunable propulsion strategy that enhances speed and spatial exploration through simultaneous and cooperative force generation.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer
Movement is a fundamental survival skill for life on Earth. From the single-celled bacteria crawling across a leaf to the white blood cells hunting down an infection in a human body, the ability to move allows organisms to find food, escape danger, and interact with their neighbors. While many creatures rely on a single method of locomotion, such as the whip-like tail of a bacterium or the muscular contraction of an animal cell, nature often provides a backup plan. Many organisms possess multiple, distinct engines for movement, each evolved at different times and built from different parts. For decades, scientists have wondered how a single cell manages these different engines. Do they switch back and forth, using one while the other rests? Or do they somehow combine them to move faster and more efficiently? Understanding how these separate systems work together could reveal a hidden layer of complexity in how life adapts to its environment.
In a new study, researchers focused on a predatory soil bacterium called Myxococcus xanthus to answer this question. This bacterium is a master of surface travel, equipped with two very different motors. The first, known as A-motility, works like a series of tiny, sticky feet that grab the ground and pull the cell forward. The second, called S-motility, uses long, hair-like filaments called pili that shoot out, grab onto the surface, and then reel the cell in, much like a fishing line. For a long time, scientists believed these two systems were segregated: the sticky-foot motor was thought to be used by solitary scouts, while the fishing-line motor was reserved for groups of cells moving together. However, the new research challenges this old view, showing that a single bacterium can run both engines at the same time.
To see this in action, the team developed a high-tech way to watch individual bacteria move under a microscope. They used special fluorescent tags to light up the sticky feet and the fishing-line filaments, allowing them to track both systems simultaneously as the bacteria moved across a surface. What they found was surprising. Instead of taking turns, the bacteria often engaged both motors at once. When they did, the cells moved significantly faster than when they used just one system alone. In fact, the speed of these dual-engine bacteria was more than the simple sum of the two separate motors, suggesting that the two systems were working together in a way that amplified their power.
The researchers also discovered that the bacteria could tune this dual-engine system based on their environment. By changing the amount of calcium in the water surrounding the cells, they could shift the balance between the two motors. In low calcium, the bacteria relied mostly on the sticky-foot motor. As the calcium levels increased, the fishing-line motor became more active, eventually taking over as the primary driver of movement. This ability to smoothly transition from one mode to another, or to blend them, gave the bacteria a versatile toolkit for navigating complex terrains.
Perhaps the most unexpected finding was that the two systems could help each other even when one wasn't directly touching the ground. The researchers created a mutant bacterium that had a working sticky-foot motor but lacked the ability to stick to the surface. Even without the ability to anchor itself, this mutant still moved faster than a bacterium that lacked the sticky-foot motor entirely. This suggests that the presence of the second motor, even if it isn't currently pulling on the ground, somehow makes the fishing-line motor more efficient. It is as if the two engines are linked, where the activity of one boosts the performance of the other, creating a synergy that allows the cell to explore its world more effectively than either system could on its own.
This study reveals that Myxococcus xanthus does not simply choose between different ways to move; it integrates them into a single, flexible strategy. By running both motors simultaneously and adjusting their balance based on chemical signals in the environment, the bacteria achieve a level of performance that is greater than the sum of its parts. This discovery changes how we understand bacterial movement, showing that even single cells can coordinate complex, multi-engine systems to solve the challenges of their environment. It suggests that the ability to combine different evolutionary tools might be a common strategy for life, allowing organisms to adapt and thrive in a changing world.
Drowning in papers in your field?
Get daily digests of the most novel papers matching your research keywords — with technical summaries, in your language.