Multicellular Life Evolves in Laboratory
An evolutionary transition that took several billion years to occur in nature has happened in a laboratory, and it needed just 60 days. Under artificial pressure to become larger, single-celled yeast became multicellular creatures. That crucial step is responsible for life’s progression beyond algae and bacteria, and while the latest work doesn’t duplicate prehistoric transitions, it could help reveal the principles guiding them.
In the new study, researchers led by evolutionary biologist Michael Travisano of the University of Minnesota and William Ratcliff grew brewer’s yeast, a common single-celled organism, in flasks of nutrient-rich broth. Once per day they shook the flasks, removed yeast that most rapidly settled to the bottom, and used it to start new cultures. Free-floating yeast were left behind, while yeast that gathered in heavy, fast-falling clumps survived to reproduce. Within just a few weeks, individual yeast cells still retained their singular identities, but clumped together easily. At the end of two months, the clumps were a permanent arrangement. Each strain had evolved to be truly multicellular, displaying all the tendencies associated with “higher” forms of life: a division of labor between specialized cells, juvenile and adult life stages, and multicellular offspring.