Study Reveals Ability of Yeast to Quickly Evolve

An article on today's New York Times chronicled a fascinating study at the University of Minnesota, a study that may change the way we study evolution. In the study, students discovered that yeast cells used to brew beer can form basic bodies in approximately two weeks.

Researchers created an experiment in which brewer's yeast was fed sugar and encouraged to reproduce, in hopes that the typically unicellular organism would perhaps create some kind of multicellular creature. To encourage this evolution the scientists raised so called "lines of yeast" from a single cell in 10 individual flasks full of "broth" - a soupy substance of nutrients. The flasks were shaken constantly for twenty four hours, and then allowed to settle. One drop of settled cells were put into a new flask and the yeast grew again. This meant that if the yeast fell quickly it would have a larger chance of survival. In a few weeks Dr. Ratcliff, the leader of the study, found that the yeast cells fell rapidly and created a small cloud of yeast at the base of the container. When examined under a microscope, it appeared that the yeast was, in fact, growing in small colonies. Each of these contained hundreds of individual cells. These colonies appeared to be in the shape of snowflakes, and appeared after a mere 60 generations of cells.

One cell of yeast would grow to full size in a matter of hours. Then it's "branches" that grew outwards would cut into each other until they broke. The broken branches would then each sprout another yeast section, which would again snap. This phenomenon is not unique to yeast. A group of unicellular organisms, choanoflagellates, often grow in the same way.

The researches plan to continue their work by looking into the genomes of the new yeast organisms, attempting to find the mutation that allowed for this growth. The yeast themselves are still evolving, changing so that they may reproduce faster and grow more.

source:
http://www.nytimes.com/2012/01/17/science/yeast-reveals-how-fast-a-cell-can-form-a-body.html
http://www.scientificamerican.com/article.cfm?id=test-tube-yeast-evolve

Image courtesy of:
http://dft.ba/-yeast