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Earth’s first cells could have made specialized compartments

Earth’s first protocells could have spontaneously formed their own “bubble-like” compartments. This may give us an idea of how cell division evolved.

Image of bubbles in protocells

“Protocells” containing bubble-like compartments formed spontaneously on a mineral-like and encapsulated fluorescent dye. This could have been what happened 3.8 billion years ago when cells first began to form. Image courtesy of Karolina Spustova.

Photo of Karolina S
Dr. Karolina Spustová. Photo: K Spustová

New research by PhD student, Karolina Spustová, and colleagues in the Gözen Group at NCMM provides evidence that the “protocells” that formed on the earth's surface around 3.8 billion years ago, could have had specialized bubble-like compartments. The research has found that these compartments are thought to have formed spontaneously and encapsulated small molecules, forming “daughter” protocells. Protocells are simple, cell-like structures that formed from non-living elements, and are thought to have appeared before bacteria and single-celled organisms. 

The research has been presented by Gözen group PhD student, Karolina Spustová at the 65th Annual Meeting of the Biophysical Society. (Wednesday 24 February). The research was originally published in January 2021 in the journal Small: Subcompartmentalization and Pseudo-Division of Model Protocells

Findings shed light on how our own cells may have evolved

Scientists have long speculated about the features that our long-ago single-celled ancestors might have had and the order in which those features came about. Bubble-like compartments are a hallmark of the so-called 'superkingdom'. This is the 'taxonomic order', or classification, of living organisms that humans and many other species, including yeast, belong to. The cells in today’s superkingdom have a host of specialized molecules that help make and shape these bubbles inside our own cells. Scientists wondered what came first: the bubbles or the shaping molecules? New research by Karolina Spustova, a PhD student in the Gözen group, shows that with just a few key pieces these little bubbles can form on their own, encapsulate molecules, and divide without help.

Did protocells come before bacteria?

3.8 billion years ago is about when our long ago single-cell ancestor came to be. It would have preceded not only complex organisms in our superkingdom, but also the more basic bacteria. Whether this “protocell” had bubble-like compartments is a mystery. For a long time, scientists thought that these lipid-bubbles were something that set our superkingdom apart from other organisms, like bacteria. Because of this, scientists thought that these compartments might have formed after bacteria came to exist. But recent research has shown that bacteria have specialized compartments too, which led Gözen’s research team to wonder—could the protocell that came before bacteria and our ancestors have them? And if so, how could they have formed?

Process can be compared to cell division

The research team mixed the lipids that form modern cell compartments, called phospholipids (a main component of a cell's membrane), with water and put the mix on a mineral-like surface. They found that large bubbles spontaneously formed, and inside those bubbles, were smaller ones. To test whether those compartments could encapsulate small molecules, as they would need to do to have specialized functions, the team added fluorescent dyes. They observed that these bubbles were able to take up and hold onto the dyes. They also saw instances where the bubbles split, leaving smaller “daughter” bubbles, which is “something like simple division of the first cells,” Spustova says. All of this occurred without any molecular machines, like those we have in our cells, and without added energy.

The early earth possibly provided the right conditions for these bubble-like compartments to form spontaneously

The idea that this could have happened on Earth 3.8 billion years ago is not inconceivable. Gözen explained that water would have been plentiful, plus “silica and aluminum, which we used in our study, are present in natural rocks.” Research shows that the phospholipid molecules could have been synthesized under early Earth conditions or reached Earth with meteorites. Gözen says, “these molecules are believed to have reached sufficient concentrations to form phospholipid compartments.” So, it is possible that the ancient “protocell” that came before all the organisms currently on Earth, had everything it needed for bubble-like compartments to form spontaneously.

This article originally appeared on the BPS website: Evidence That Earth’s First Cells Could Have Made Specialized Compartments

Published Feb. 24, 2021 4:30 PM - Last modified Mar. 16, 2021 12:31 PM