‘Protocells’ show ability to reproduce

Man-made balls of genetic material and membranes can pull off a decent impression of primitive cells. 

These squishy spheres known as “protocells” can accept chemical deliveries to sustain a division process that mimics that of living cells, researchers in Japan report September 29 in Nature Communications. These cell-like creations may be a step toward making future protocells that can imitate evolution, the scientists say.

The results offer clues to how living cells developed their ability to reproduce, says study coauthor Tadashi Sugawara, a physical organic chemist at Kanagawa University in Japan. Like the cells within plants and animals, these protocells have four stages in their division process, Sugawara says. The real living cells and the protocells both have a replication stage and division stage. But instead of two growth phases, these protocells have an “ingestion” stage, in which they take in substances from their surroundings, and a “maturity” stage.

The protocells, composed of thin membranes wrapped around DNA and proteins, can expand and divide when provided with a membrane-building molecule. But new protocells quickly run out of other biochemical ingredients needed to continue reproducing. So the researchers designed membrane-wrapped delivery vessels that provide daughter protocells with additional biological building blocks. With these ingredients, the protocells can continue dividing for a third generation.

These protocells appear to require a complex design to work properly, says evolutionary biologist David Baum of the University of Wisconsin–Madison. Plus, some scientists believe cell precursors like these may not have been the first living things to undergo evolution, he says. Chemical oozes may have been able to cooperate with each other and grow more sophisticated over time, before a cell’s ancestors developed, he says.

Baum notes that the protocells in the study aren’t self-sustaining, as the researchers must replenish the system with essential chemical ingredients. The protocells also depend on fluctuations in heat and acidity to copy their genetic material and accept chemical deliveries, which makes them too artificial to be sustainable, Sugawara says. But he notes that hot, acidic environments like those around hydrothermal vents could have driven similar genetic processes in nature.

Good imitators of early cells could help scientists understand how real cells evolved, he adds. “If we could make many instances where we could get evolving protocells, and we could see what you need, that would really help us understand how that could have arisen naturally.”