Research led by the University of Auckland has unveiled significant insights into the evolutionary origins of one of nature’s earliest motors, which emerged approximately 3.5 billion to 4 billion years ago to drive bacterial movement. The study, published in the journal mBio, provides a comprehensive overview of the evolution of bacterial stators—proteins that function similarly to pistons in a car engine.
Stator proteins reside in the bacterial cell wall, converting charged particles, known as ions, into torque, enabling bacteria to swim. According to Dr. Caroline Puente-Lelievre from the School of Biological Sciences, the research elucidates how movement is fundamental to life across various organisms. She stated, “Movement is essential to life, from microbes to the largest animals. Within our cells, constant molecular motion is what keeps us alive. We’re unraveling the story of how life first got moving.”
Understanding Bacterial Propulsion
The collaborative research involved teams from UNSW Sydney and the University of Wisconsin Madison. It leveraged the groundbreaking capabilities of DeepMind AI’s AlphaFold, which predicts the three-dimensional folded structures of proteins. During Earth’s formative years—characterized by volcanic activity and frequent meteorite impacts—bacteria emerged as some of the earliest life forms, developing complex mechanisms to facilitate movement in a hostile environment.
In bacteria, stators generate the power required to turn a rotor, which spins the flagellum—a long, whip-like tail that propels the cell through liquid. To investigate the evolution of stators, researchers analyzed genomic data from over 200 bacterial genomes, constructed evolutionary trees using advanced computational tools, and modeled the 3D structures of proteins. The shape of each protein is vital to its function, emphasizing the importance of this aspect in understanding bacterial motility.
Dr. Puente-Lelievre explained, “We predicted the sequences and structures of ancestral proteins that existed millions or billions of years ago and may no longer exist.” Typically, a stator consists of five identical versions of a protein called MotA and two identical versions of another protein known as MotB. These motor proteins evolved from an ancient two-protein system, leading to the emergence of various other functions.
Insights into Protein Evolution
Senior researcher Dr. Nick Matzke of the University of Auckland noted, “This supports the idea that complex machines evolve by coopting simpler machines with simpler functions.” He likened this process to the evolutionary development of protofeathers in dinosaur ancestors, which initially served to retain heat and later adapted for gliding or flying. Similarly, ancient bacteria repurposed an ion flow mechanism into one of nature’s most enduring engines.
The researchers compared 3D protein structures to identify distinguishing features among similar proteins, particularly those unique to stators, such as regions responsible for generating torque. Dr. Puente-Lelievre remarked, “Finally, we performed functional assays in the lab. 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 evolution, the fundamental characteristics of these microscopic engines have remained largely unchanged. Assistant Professor Matthew Baker from UNSW Sydney highlighted the current advancements in structural biology and microbiology, stating, “We live in a remarkable era… where new sequences are discovered daily, and tools like AlphaFold let us near instantly explore possible protein structures.”
This research not only sheds light on the origins of bacterial motility but also illustrates the potential of modern scientific tools in uncovering ancient biological secrets, paving the way for deeper understanding of life’s evolutionary history.
