A Nobel laureate biologist, two engineering institutions, and a sample of Houston rainwater provide fresh insights into the origins of life on Earth that is this new research suggests rainwater helped form the first protocell walls
| Date | August 21, 2024 |
| Source | University of Chicago |
| Summary | Recent studies suggest that rainwater might have played a crucial role in the development of a protective mesh-like wall around protocells 3.8 billion years ago. This discovery represents a vital step in the evolution from tiny RNA droplets to the complex organisms that include bacteria, plants, animals, and humans. |
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How new research suggests rainwater helped form the first protocell walls
One of the biggest unanswered questions about the origin of life is how free-floating RNA droplets in the primordial soup evolved into membrane-bound structures, known as cells. This new research has answered it.
A new study published today in Science Advances, UChicago PME postdoctoral researcher Aman Agrawal, along with co-authors including UChicago PME Dean Emeritus Matthew Tirrell and Nobel Prize-winning biologist Jack Szostak, demonstrate how rainwater might have contributed to forming a mesh-like wall around protocells 3.8 billion years ago. This step was crucial in the transition from simple RNA droplets to the complex life forms we know today.
The research focused on “coacervate droplets”—naturally occurring clusters of complex molecules like proteins, lipids, and RNA. These droplets act like oil in water and have long been considered potential candidates for protocells. However, a significant issue remained: the droplets exchanged molecules too quickly. This rapid exchange meant that any new RNA mutations would be shared among all the droplets, preventing differentiation, competition, and, ultimately, evolution.
Without differentiation, life as we know it couldn’t arise.
“If molecules continuously swap between droplets or cells, they all become identical, preventing evolution from taking place,” Agrawal explained.
“Engineers have been studying the physical chemistry of these complexes and polymer chemistry for years,” Szostak noted. “When exploring something as complex as the origin of life, it’s crucial to involve experts from different fields.”
“DNA encodes information but doesn’t perform any functions, while proteins perform functions but don’t carry hereditary information,” Agrawal explained.
Researchers theorized that RNA emerged first, performing both roles, with proteins and DNA evolving later. This made RNA a strong candidate for the first biological material, and coacervate droplets an ideal candidate for the first protocells—until Szostak’s 2014 study showed that RNA exchanged too rapidly within the droplets.
“You can create various types of coacervates, but they don’t maintain separate identities. RNA content exchanges too quickly, which has long been a problem,” Szostak said. “Our new research shows that this issue can be partially resolved by placing the coacervate droplets in distilled water, like rainwater. This process forms a tough outer skin that limits RNA exchange.”
Agrawal first experimented with coacervate droplets and distilled water and studied their behavior under an electric field. Though initially unrelated to the origin of life.
Using Szostak’s RNA samples, Agrawal found that transferring coacervate droplets into distilled water extended the RNA exchange timeframe from minutes to days—enough time for mutations, competition, and evolution.
“If protocell populations are unstable, they share genetic material and become clones. For evolution to happen, they need to stabilize long enough for mutations to take hold,” Agrawal said.
Although Agrawal initially used deionized water, journal reviewers questioned whether ancient rainwater’s acidity would alter results. To address this, the team collected rainwater in Houston and tested the droplets’ stability in both real rainwater and lab-modified water. The results were consistent: mesh-like walls :formed, creating conditions conducive to life.
While the rainwater of today isn’t identical to that of 3.8 billion years ago, the study shows that these conditions are possible, bringing researchers closer to understanding how protocells evolved.
FAQ:
1. What is the first cell in biology?
The first cell refers to the earliest form of a cell that existed on Earth, often called the protocell. These early cells are believed to have formed around 3.5 to 4 billion years ago. They were the precursor to all life forms.
2. What are protocells?
Protocells are simple, membrane-bound structures that exhibit some characteristics of living cells but lack complex internal organization. They are considered precursors to true cells.