Synthetic Biology Sheds Light on Microbial Evolution

Researchers are leveraging synthetic biology to reconstruct ancient microbial processes and observe evolutionary transitions in real-time, bridging the gap between Earth's earliest life forms and modern biotechnology. By engineering organisms with ancestral genes and conducting long-term evolutionary experiments, scientists are uncovering the fundamental design rules of life, such as the emergence of multicellularity and metabolic dependencies. This research provides the synthetic biology sector with critical insights into how environmental pressures shape biological functions, offering a foundation for more predictable and sophisticated organism engineering.

Betül Kaçar, Ph.D., of the University of Wisconsin-Madison and Director of the NASA MUSE consortium, is using synthetic biology to investigate the co-evolution of life and the planet. Her lab reconstructs ancient microbial genes inferred from modern sequence data and evolutionary modeling, then inserts this synthesized DNA into living microbes to compare phenotypic outcomes with geological evidence from the rock record. This work focuses on the three key features of life—a genome, a metabolic network, and membrane-bound compartmentalization—to understand how ancient metabolic processes, such as oxygenic photosynthesis, fundamentally altered Earth's environment from anoxic to oxic states approximately 4 billion years ago.

The transition from unicellular to multicellular life is being studied through the Multicellularity Long Term Evolution Experiment (MuLTEE), led by William Ratcliff, Ph.D. Over more than 10,000 generations, researchers have observed snowflake yeast (Saccharomyces cerevisiae) evolve from fragile single cells into large, branching clusters that are as strong as wood and show signs of cellular specialization. Ratcliff posits that the capacity for multicellularity may be a common feature across biological lineages, suggesting that the transition is driven primarily by environmental pressures rather than rare, intrinsic genetic hurdles, a hypothesis currently being tested through further synthetic manipulation of cellular division of labor.

Synthetic biology is also exposing gaps in the understanding of modern microbial metabolism, which is essential for future biotechnological applications. Jeffrey Gralnick, Ph.D., at the University of Minnesota, attempted to engineer the iron-oxidizing bacterium Mariprofundus ferrooxydans to utilize sugars like xylose and glucose, similar to Escherichia coli. While the engineered bacteria successfully gained the ability to process these sugars, they remained unexpectedly dependent on their native iron-based energy metabolism, a result that contradicted researchers' predictions. This highlights the complexity of metabolic networks and demonstrates how synthetic biology acts as a powerful tool for uncovering the fundamental biological principles that govern both ancient and contemporary organisms.