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Schizosaccharomyces pombe

life science Maturity 11-13 Next article →

Schizosaccharomyces pombe is a species of unicellular eukaryote commonly known as fission yeast. It is a single-celled fungus that belongs to the division Ascomycota. This division is the largest and most diverse group of fungi in the world. Scientists use fission yeast as a model organism to study molecular and cell biology. This means they observe its simple life to understand complex biological processes. It is especially useful for studying how cells grow, divide, and respond to damage. Because it is a eukaryote, its cellular machinery is similar to that of more complex life forms.

Fission yeast division
Fission yeast division

The cell of S. pombe has a distinct rod shape. These cells typically measure 3 to 4 micrometres in diameter. They are usually between 7 and 14 micrometres in length. Unlike many other cells, they maintain this shape by growing exclusively at the cell tips. To reproduce, the yeast undergoes a process called medial fission. This means the cell splits exactly at its midpoint. This process produces two daughter cells that are equal in size. This predictable division makes it a powerful tool for researchers studying the cell cycle.

fission yeast cytokinesis
fission yeast cytokinesis

The life cycle of fission yeast involves several distinct stages. First, the cell enters the S phase, also called the Synthetic phase. During this stage, the cell performs chromosome duplication. Following this, the cell enters the M phase, or Mitotic phase. This phase includes mitosis, where chromosomes are segregated, and cytokinesis, where the cell physically divides. There are also gap phases called G1 and G2. In S. pombe, the G2 phase is particularly extended. The cell stays in G2 for a long time to ensure it has reached the correct size before it divides. The cell cycle progression is also influenced by nutrients. In poor nutrient conditions, cells grow slowly and take longer to double in size.

fission yeast cell size
fission yeast cell size

History shows how this yeast moved from breweries to laboratories. It was first isolated in 1893 by Paul Lindner. He found it in millet beer imported from East Africa. The species name "pombe" is the Swahili word for beer. In the 1940s, Urs Leupold isolated standard strains for research. During the 1950s, Leupold used the yeast to study genetics. At the same time, Murdoch Mitchison used it to study the cell cycle. Later, researcher Paul Nurse merged these two fields of study. His work on cell cycle regulation led to a Nobel Prize in Physiology or Medicine in 2001. He shared this honor with Lee Hartwell and Tim Hunt.

Schizosaccharomyces pombe tsentrosoom
Schizosaccharomyces pombe tsentrosoom

The genetic significance of S. pombe is immense. Its genome consists of approximately 14.1 million base pairs. This genome contains about 4,970 protein-coding genes and at least 450 non-coding RNAs. In 2002, a consortium led by the Sanger Institute published its full genome sequence. This made it the sixth model eukaryotic organism to be fully sequenced. Researchers have identified that 70% of its genes are orthologous to human genes. This means they are similar to genes found in humans. Because of this connection, S. pombe helps scientists study genes involved in human diseases. It is also used to study how cells respond to DNA damage and replication.

Fission yeast division
Fission yeast division

There are many different natural strains of this yeast. Approximately 160 strains have been isolated from various locations globally. These include regions in Europe, Asia, and the Americas. Many strains come from cultivated fruits like apples and grapes. They are also found in alcoholic beverages like Brazilian Cachaça. S. pombe is even present in kombucha, which is a fermented tea. While it is found in these places, scientists are still studying its exact natural ecology. Some strains can even degrade L-malic acid, an organic acid found in wine.

fission yeast cytokinesis
fission yeast cytokinesis

Comparing S. pombe to other yeasts provides deeper insight into its unique traits. It is often compared to Saccharomyces cerevisiae, known as budding yeast. These two species diverged about 300 to 600 million years ago. While they are both yeasts, they have many differences. S. pombe has only 3 chromosomes, while S. cerevisiae has 16. S. pombe is usually haploid, meaning it has one set of chromosomes. It also has nearly 5,000 introns, which are segments of DNA. This is much higher than the 250 introns found in S. cerevisiae. These differences allow scientists to choose the best organism for specific biological questions.

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File:Schizosaccharomyces pombe tsentrosoom.jpg
Schizosaccharomyces pombe tsentrosoom.jpg
File:Fission yeast division.jpg
Fission yeast division.jpg
File:fission yeast cytokinesis.jpg
fission yeast cytokinesis.jpg
File:fission yeast cell size.jpg
fission yeast cell size.jpg
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