Scientists have unveiled a groundbreaking prototype cell, named 'SpudCell', which represents a significant leap forward in the field of synthetic biology. Developed by Kate Adamala and her team at the University of Minnesota, this engineered cell can perform some fundamental functions of life, such as copying DNA and dividing, albeit in a rudimentary fashion and with considerable external support.
The SpudCell was constructed using just 36 genes, predominantly sourced from E. coli bacteria, supplemented with genetic material from phage viruses and a gene for a fluorescent protein from jellyfish to aid visibility. This approach contrasts sharply with previous attempts to understand minimal life forms, which typically involved systematically removing genes from existing bacteria. For instance, in 2016, a bacterium with 901 genes was reduced to 473. The SpudCell project started with a minimalist design, building upwards from a core set of essential genes.
While impressive, the researchers are cautious about labelling the SpudCell as truly 'alive'. It requires a constant external supply of DNA and protein building blocks, as well as fatty molecules to form its cell-like structure. Despite demonstrating a form of evolution where deliberately introduced beneficial mutations improved cell performance, it cannot generate spontaneous mutations or sustain indefinite replication. Adamala herself states that for it to be considered living, it would need to replicate indefinitely and be capable of Darwinian evolution.
The assembly process involved engineering the 36 genes into seven circular pieces of DNA. These were then combined in a solution with other necessary components, allowing them to spontaneously form cell-like bubbles. Two genes code for proteins that create pores in the cell membrane, facilitating the entry of small molecules, while larger molecules are supplied via fusing bubbles. Division occurs when large proteins bind to these pores, causing the membrane to bend and bud off new, often unequally sized, 'daughter' cells with a random assortment of the genetic material.
The cells' inability to divide indefinitely, typically stopping after around five rounds, is believed to be due to their lack of protein-making factories, known as ribosomes. The University of Minnesota team has made the SpudCell project open source, inviting global collaboration to further develop its capabilities and potentially overcome current limitations, such as achieving indefinite division and consolidating all genes onto a single, more manageable piece of DNA.