Proto-Cell Formation

Darren Orf, "This Could Be How the Earth’s First Cells Formed"

The answer may have been hiding in our own bodies all along.

Because phosphates lie at the heart of almost every chemical reaction in the human body, scientists from California-based Scripps research had a hunch that a phosphate process known as “phosphorylation” occurred earlier in Earth’s history than we previously realized. Exploring this theory, scientists recreated the conditions of early Earth and were able to transition fatty acids into a phospholipid membrane surrounding vesicles, a stable platform for future chemical reactions. This discovery highlights a possible pathway that nature took on its way to creating complex lifeforms on Earth.

Everyone wants to know the answer to how life began on Earth, but few people are as singularly focused on the question as Ramanarayanan Krishnamurthy.

As a chemist at the California-based Scripps Research, Krishnamurthy has investigated the rise of RNA, the bridge between prebiotic chemistry to protobiology, and the complex emergence of protocells—a kind of ancestor of cells that make up all living things. Krishnamurthy even co-leads a NASA Astrobiology initiative investigating the origins of life on Earth.

Now, Krishnamurthy and his team have potentially uncovered another missing piece of Earth’s biological puzzle: the method behind the formation of the very first cells. In a new paper published in the journal Chem, scientists discovered that a process called “phosphorylation”—when a phosphate group is attached to a molecule—could have occurred much early in Earth’s history, and created a pathway for the creation of protocells from fatty acids.

We’ve now discovered a plausible way that phosphates could have been incorporated into cell-like structures earlier than previously thought, which lays the building blocks for life,” Krishnamurthy said in a press statement. “This finding helps us better understand the chemical environments of early Earth so we can uncover the origins of life and how life can evolve on early Earth.”

The big question for Krishnamurthy and his team, according to the researchers, was trying to figure out how these protocells transitioned to a double chain of phosphates—a structure that is more stable and can create chemical reactions. To understand this, the team recreated the conditions of early Earth in the lab by using chemicals such as fatty acids and glycerol. These mixed solutions were cooled, heated, and shaken to stimulate chemical reactions. They were also tested with different ratios, temperatures, and pH levels to investigate how these structures form. By also including dyes, the researchers could witness the formation of vesicles, which are similar to protocells.

It turns out the fatty acids were able to transition to a “phospholipid environment,” suggesting that phosphorylation could have taken place much earlier than previously believed. The theory of this process occurring so early is backed up by the fact that phosphates are present “in nearly every chemical reaction in the body,” according to the press statement. Because of this, the likelihood of them playing a critical role in the development of life on Earth was pretty high.

“We’ve discovered one plausible pathway for how phospholipids could have emerged during this chemical evolutionary process,” Scripps research biophysicist Ashok Deniz said in a press statement. Phospholipids are a further evolved vesicle membrane. “It’s exciting to uncover how early chemistries may have transitioned to allow for life on Earth. Our findings also hint at a wealth of intriguing physics that may have played key functional roles along the way to modern cells.”

While this is an important step in understanding the complex chemistry that eventually gave rise to Earth’s stunning biodiversity, scientists still have a long way to go before confidently uncovering the whole story. For Krishnamurthy, and the rest of his team, the work continues.