Which fission yeast species is a major model organism in cell biology?

The major fission-yeast model organism in cell biology is Schizosaccharomyces pombe.

Unlike budding yeast, S. pombe grows mainly from its cell tips and divides across the middle by fission, producing two daughter cells of roughly equal size. Its rod-shaped cells and predictable division cycle make processes such as chromosome segregation, cytokinesis, and cell-size control unusually easy to observe under a microscope.

The species was isolated in 1893 by Paul Lindner from East African millet beer. Its name reflects that origin: pombe is a Swahili word for beer, while schizo refers to splitting or fission. The organism became a modern experimental model through genetic and cell-cycle work in the mid-twentieth century, including research by Urs Leupold and Murdoch Mitchison.

S. pombe is not the same yeast as Saccharomyces cerevisiae, the familiar budding yeast. It has about 14.1 million base pairs, only three chromosomes, and many genes with counterparts in humans. Work with fission yeast helped reveal conserved cell-cycle mechanisms; Paul Nurse shared the 2001 Nobel Prize in Physiology or Medicine for discoveries concerning cell-cycle regulation.