Studies on Tetrahymena have contributed to several scientific milestones Including.

http://en.wikipedia.org/wiki/Tetrahymena

1. First cell which showed synchronized division, which led to the first insights into the existence of mechanisms which control the cell cycle.
2. Identification and purification of the first cytoskeleton based motor protein such as dynein.
3. Aid in the discovery of lysosomes and peroxisomes.
4. Early molecular identification of somatic genome rearrangement.
5. Discovery of the molecular structure of telomeres, telomerase enzyme, the templating role of telomerase RNA and their roles in cellular senescence and chromosome healing (for which a Nobel Prize was won).
6. Nobel Prize winning co-discovery (1989, in Chemistry) of catalytic ribonucleic acid (ribozyme).
7. Discovery of the function of histone acetylation.
8. Demonstration of the roles of posttranslational modification such as acetylation and glycylation on tubulins and discovery of the enzymes responsible for some of these modifications (glutamylation)
9. Crystal structure of 40S ribosome in complex with its initiation factor eIF1
10. Discovery of self-splicing RNA