Research from the University of Auckland has uncovered significant insights into the evolutionary origins of one of nature’s earliest motors, which emerged between 3.5 billion and 4 billion years ago. Scientists have detailed the development of bacterial stators, essential proteins that function similarly to pistons in a car engine, providing propulsion for bacteria to navigate their environments. The findings were published in the journal mBio.
Dr. Caroline Puente-Lelievre, from the School of Biological Sciences, explained that stator proteins reside within the bacterial cell wall, converting charged particles, or ions, into torque that enables bacterial movement. This evolutionary leap likely stemmed from ion transporter proteins, which are common in bacterial membranes. “Movement is essential to life, from microbes to the largest animals,” stated Puente-Lelievre. “We’re unraveling the story of how life first got moving.”
Understanding Ancient Bacterial Mechanics
The study, conducted in collaboration with UNSW Sydney and the University of Wisconsin Madison, leveraged the advances made by DeepMind AI through its AlphaFold technology. This breakthrough allows for the prediction of the three-dimensional shapes of proteins, crucial for understanding their functions.
Bacteria, some of the earliest life forms on Earth, thrived in a harsh environment characterized by volcanic activity and meteorite impacts. During this tumultuous period, they evolved sophisticated mechanisms, including a built-in motor system. In bacterial cells, stators provide the necessary power to rotate a rotor, which in turn spins the flagellum—a structure that enables the bacteria to swim, functioning much like a miniature propeller.
To investigate the evolution of stators, researchers analyzed genomic data from over 200 bacterial genomes. They employed advanced computational tools to construct evolutionary trees and model the three-dimensional structures of proteins. The shape of each protein is critical, as it directly influences its functionality.
Tracing the Evolution of Stator Proteins
The research team predicted the sequences and structures of ancestral proteins that may have existed millions or even billions of years ago. According to Puente-Lelievre, a typical stator comprises five identical MotA proteins and two MotB proteins. These “motor proteins” originated from an ancient two-protein system that later developed additional functions. Dr. Nick Matzke, a senior researcher at the University of Auckland, remarked, “This supports the idea that complex machines evolve by co-opting simpler machines with simpler functions.”
Drawing parallels to evolutionary traits in other species, Matzke noted that just as the ancestors of birds evolved protofeathers for warmth and later adapted them for flight, ancient bacteria repurposed tools for ion transport into a new function: movement.
The research team also compared the three-dimensional protein structures to discern key differences and unique traits of stators, particularly regions responsible for generating torque. “Finally, we performed functional assays in the lab,” Puente-Lelievre explained. “We took E. coli bacteria that lacked the torque-generating interface and found that none of them could swim, confirming that this specific region is essential for movement in this group of bacteria.”
Despite billions of years of evolutionary changes, the fundamental features of these microscopic engines have remained largely unchanged and continue to play a vital role in life today. Assistant Professor Matthew Baker from UNSW Sydney expressed optimism about the current era of structural biology, stating, “We live in a remarkable era where new sequences are discovered daily and tools like AlphaFold allow us to explore possible protein structures almost instantly.”
These findings not only enhance our understanding of bacterial evolution but also underscore the enduring significance of these ancient mechanisms. The research sheds light on the complex history of life on Earth, revealing how simple biological functions can evolve into sophisticated systems that sustain movement and life itself.
