2. Yeasty Beasties in the Tree of Life A project with Katie Grover and Debra Lowe

3. A long time ago in a laboratory far, far away, scientists found that many species of yeast were related. They used every means at their disposal to find exactly how the species tied together. They found many likely scenarios, but still the true phylogeny was just out of reach… until now.

4. As our story begins… We have a good idea how yeasts are related, but there is some disagreement when looking at specific species. Also, not all of the species we’re working with have been clearly placed in the tree of life. What are we to do? Kluveromyces, Saccharomyces, Torulaspora and Zygosaccharomyces from International Journal of Systematic Bacteriology Apr 1997 453-460 Vol 47 James et al. “A Phylogenetic Analysis of the Genus Saccharomyces Based on 18S rRNA Gene Sequences: Description of Saccharomyces kunashirensis sp. nov. and Saccharomyces martiniae sp. nov. * * * * *

5. The Problem Most twigs of the phylogenetic tree have been placed using only one rRNA subunit to determine relatedness. Other trees may have been analyzed using a different subunit, causing differences in the details of the two trees.

6. So… Wouldn’t it be more accurate to use two rRNA subunits? Yes, but… In the past, this was rarely done because of a lack of information and resources. Not enough DNA sequences had been processed to effectively analyze at two subunits. Also it was difficult to resolve apparent conflicts between the two systems.

7. Our Goal … is to create a more accurate phylogenetic tree of yeast species using analysis of two ribosomal subunits as our basis of comparison

8. More Specifically (18S) and (26S) subunits will be analyzed in approximately 50 species of yeasts, including many Kluyveromyces, Saccharomyces, Torulaspora and Zygosaccharomyces species.