Summary written for researchers on The Bond Lab. See Science and the Biotic SpudCell page for primary reporting and the manuscript.
SpudCell: A synthetic cell on the verge of life
SpudCell ate, grew, and divided. Kind of.
A team at the University of Minnesota has built a microscopic blob of mostly water, wrapped it in a fatty skin, and watched it do something that genuinely surprised the people who build this kind of thing for a living: feed itself, copy its genes, and split in two. They called it SpudCell, partly because it is round and a bit ugly, and partly because it echoes Sputnik, the first manufactured thing to make a scientist’s hands shake.
The work, from Kate Adamala’s lab, sits inside a corner of biology called bottom-up synthetic biology. The pitch is simple to state and brutal to execute: take the pieces of life off the shelf, dump them into a container, and see if container-level behaviours like metabolism, growth, and division emerge. Not edit an existing cell. Not slip a few new genes into E. coli. Build the cell from non-living parts.
Building a cell from non-living parts
SpudCell is a water-in-oil droplet, smaller than a bacterium, with a lipid membrane around it. Inside, the team packed PURE, the cell-free protein synthesis kit that biologists use when they want ribosomes to read DNA and make proteins outside an actual cell. They added a stripped-down genome of 36 genes, about fifty times smaller than what even the most minimal known bacteria carry. Then they wrote that genome so it encodes its own growth and division machinery.
Growth and feeding
Growth is the easy part to explain. The genome codes for molecular tags that stick out of the membrane. In the surrounding fluid, the researchers sprinkled “feeder vesicles” carrying enzymes and raw materials. The tags grab the vesicles, the vesicles dump their contents inside, the droplet gets bigger. Once it has more raw materials, it can also copy its own genome.
Division by membrane repulsion
Division is where the story gets weird. The genome also codes for FLAG peptide tags on the membrane. When the team added a protein called streptavidin, those tags bound it. The bound tags repelled each other, and that physical force pinched the droplet in two. In later cycles, the daughter droplets got so small and floppy that the researchers had to push them through a membrane with tiny holes just to make the split stick.
It works. Sort of.
Efficiency, ribosomes, and engineered selection
After five rounds, only about thirty percent of the daughter droplets still carried a complete copy of the genome. The ribosomes inside slowly degrade, and there is no system in the cell to make new ones. The cells do not evolve on their own. When the team wanted to test whether a SpudCell carrying a mutation could outcompete its unmutated siblings, they had to put the mutation in by hand. It did, by the way. A tweaked version with more surface tags ended up in sixty percent of the genomes after five cycles.
Not a living cell — but a real milestone
Adamala is clear this is not a living cell. “This is like the spark,” she told Science magazine. Drew Endy at Stanford praised the decision to release the work quickly, and a few colleagues called the paper “stunning.” Seraphine Wegner at the University of Münster was more measured: “It’s a very cool paper. But I don’t think it means we’re close to creating a fully synthetic cell.”
Publication path and Biotic
The publication path was unusual. The manuscript is roughly 190 pages long. Cell rejected it. One reviewer reportedly wrote that “SpudCells were not real biology.” Adamala sent the paper to journalists under embargo before uploading it to a preprint server, which several researchers described as an odd way of doing things. The paper is headed to a new journal soon.
She has also used the moment to launch Biotic, a public-benefit research institute with about ten million dollars in seed funding, to push this corner of the field forward. The bet is that once you can build a cell from non-living parts and have it do anything on its own, you can iterate, and the sparks come faster.
Where the field stands
The honest read is somewhere in the middle. On one side, this is the first time anyone has stitched together a system that handles growth, genome replication, and division in a synthetic cell, and people in the field have been waiting for that integration. On the other side, the system needs hand-holding at almost every step. The ribosomes decay. The division is inefficient. The “evolution” is engineered in. Calling it the first synthetic cell would be generous. Calling it a real step forward is fair.
SpudCell does not change the world this week. It does change the kind of question a lab can credibly ask next month.