Cell-like bubbles that can grow and self-replicate like living cells have been created for the first time. The experiments may help to solve one of the enduring mysteries of evolution: how the first cells reproduced.

In the quest to build a basic cell from scratch, molecular biologists have found it hard to create cells that carry information about themselves and use this for replication, as living cells and their information-carrying DNA do. What nature evolved over billions of years, mere humans are struggling to copy.

But scientists in Japan have made a breakthrough. They have made giant cell-like bubbles called vesicles that can grow and split into new versions of themselves. And the crucial new ingredient that makes this work is DNA.

Tadashi Sugawara from the University of Tokyo and his team made their bubbles from fatty molecules in solution, which stuck together to form water-filled vesicles.


However, the team also added short pieces of DNA along with chemical building blocks that can make DNA copies in a process known as a polymerase chain reaction (PCR).

Quick copy

The mechanism is relatively straightforward. Each DNA piece is charged and attracts the oppositely charged fatty molecules, which form a vesicle around the DNA. The team then triggers the PCR copying mechanism, generating extra copies of the DNA inside the vesicle, which attach to the walls.

The team then added extra fatty molecules, which bind to the vesicle where the new DNA pieces are embedded in the membrane. The extra fatty molecules surround the new DNA pieces, forming daughter vesicles that eventually break away from the mother.

The result is an identical copy of the mother cell, down to the DNA it contains. Sugawara’s team call the new vesicle a “protocell” because it mimics the behaviour of real cells.

Evolution, sort of

The DNA is crucial. In theory, the vesicles could self-replicate without DNA, but it would happen much more slowly. This advantage creates a primitive form of evolution, says synthetic biologist Manuel Porcar from the University of Valencia in Spain, who wasn’t involved in the work. “After a while there are many more protocells with DNA in than without.”

Porcar says the work is important because it links DNA replication and vesicle self-replication for the first time. It’s a key moment in the field of synthetic biology, he says.

Sugawara sees many similarities between his protocell and a primitive natural cell such as the bacterium Escherichia coli. His protocells don’t have proteins, but the small molecules used to build them seem to be cooperating and working just as a protein in a cell might, he says. “Our model might suggest how a sophisticated cell could evolve.”

Journal reference: Nature Chemistry, DOI: 10.1038/nchem.1127