Scientists have created new artificial microbes by combining two very different organisms into one functioning entity. The hybrid of a yeast and a bacterium adds evidence to a long-standing hypothesis on how advanced life may have evolved.

Inside the cells of complex lifeforms are tiny, separate organs called organelles, some of which have their own separate genomes to that of the larger organism. That includes the mitochondria in animals and chloroplasts in plants, both of which generate energy for the organism. A leading theory suggests that these organelles were originally separate microorganisms that were engulfed by other cells, and the two eventually entered a symbiotic relationship that paved the way for complex life to evolve.

And now a new study has recreated this process, known as endosymbiosis. Researchers from the University of Illinois Urbana-Champaign designed and engineered artificial hybrids of two microbes – a budding yeast and photosynthetic cyanobacteria.

The resulting chimera was able to photosynthesize like the bacteria to generate energy, and reproduced through budding like the yeast. The organisms were able to propagate for at least 15 to 20 generations, and the team says that the achievement lends weight to the hypothesis that complex life got its start through endosymbiosis.

“We have essentially converted a nonphotosynthetic organism into a photosynthetic, chimeric life form,” said Angad Mehta, lead researcher on the study. “I believe that our new ability to build controlled, synthetic endosymbiotic chimera that can be genetically and metabolically manipulated, analytically studied and imaged, and computationally modeled and predicted will break the gridlock on our understanding of this remarkable evolutionary transformation.”

This isn’t the first engineered hybrid to demonstrate endosymbiosis in action. A previous study in 2018 combined yeast and E. coli in a similar fashion, tweaking each so that the bacteria had to source vitamins from the yeast and the yeast had to source energy from the bacteria.

The new research was published in the journal Nature Communications.