Schizosaccharomyces pombe

Instead of producing a small bud, its rod-shaped cell divides across the middle.

That visible relationship between growth and division has made it a useful organism for studying the cell cycle.

A growing cell lengthens at its tips while its width stays relatively constant.

After division, growth normally starts at the older end inherited from the mother cell; the newly formed end begins to grow later.

This transition from one growing end to two is called new-end take-off.

During mitosis, the nuclear envelope remains intact while the nucleus divides.

A cross-wall, or septum, then forms near the cell’s midpoint and is split to release two nearly equal daughters.

An actin–myosin ring and deposition of new wall material help organise this separation.

S. pombe usually grows as a haploid, carrying one chromosome set, although diploid cells can also be maintained in the laboratory.

Nutrient shortage can prompt compatible haploid cells to mate, joining their cells and then their nuclei.

The resulting diploid zygote normally enters meiosis and forms four haploid spores inside an ascus, the enclosing spore sac.

When returned to favourable growth conditions, the spores germinate into growing cells.

Some strains can switch mating type within a clone, while others require a partner of the opposite type.

S. pombe can ferment sugars and has been reported from fruit and fermented products, including kombucha and molasses-based fermentations.

A 2014 genomic study examined culture-collection strains originating from Africa, Europe, Asia, and Central and South America, as well as strains with unknown origins.

These collection records show varied origins, not the yeast’s abundance in every environment within those regions.

Experiments with the cell-division protein Fic1 showed that deleting its gene left many daughter cells unable to restart growth at their new ends.

This links the completion of one division to the growth pattern of the next generation.

Comparing genomes also opens a different window on its biology: Fawcett and colleagues found reduced sequence variation in several kinds of noncoding DNA relative to synonymous sites in genes.

They interpreted this as evidence that some DNA outside protein-coding sequences is constrained by biological function.

A haploid fission-yeast cell in G2 has replicated chromosomes; DNA replication does not itself make the cell diploid.

The laboratory explanation distinguishes a single nucleus with replicated DNA from a cell still containing two post-mitotic nuclei, even when their total DNA signals coincide.

The Fic1 result concerns defined laboratory mutants and comparison cells, not a claim that all naturally occurring S. pombe cells fail at new-end growth.

The publisher’s 2013 correction repaired corrupted tea1 deletion notation and adjacent missing text; the inspected article is the corrected HTML version.

The 2014 survey sequenced 32 culture-collection strains and found geographic origins only weakly reflected in their genetic grouping.

Its inference about functional noncoding DNA rests on comparisons of sequence diversity, not direct experimental validation of every noncoding region.