title: Apoptosis at inflection point in liquid culture of budding yeasts.
abstract: Budding yeasts are highly suitable for aging studies, because the number of bud scars (stage) proportionally correlates with age. Its maximum stages are known to reach at 20-30 stages on an isolated agar medium. However, their stage dynamics in a liquid culture is virtually unknown. We investigate the population dynamics by counting scars in each cell. Here one cell division produces one new cell and one bud scar. This simple rule leads to a conservation law: "The total number of bud scars is equal to the total number of cells." We find a large discrepancy: extremely fewer cells with over 5 scars than expected. Almost all cells with 6 or more scars disappear within a short period of time in the late log phase (corresponds to the inflection point). This discrepancy is confirmed directly by the microscopic observations of broken cells. This finding implies apoptosis in older cells (6 scars or more).
authors.affiliation: Graduate School of Science and Technology, Shizuoka University, Hamamatsu, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Hagiwara
authors.forename: Takashi
authors.initials: T
authors.lastname: Ushimaru
authors.forename: Kei-ichi
authors.initials: K
authors.lastname: Tainaka
authors.forename: Hironori
authors.initials: H
authors.lastname: Kurachi
authors.forename: Jin
authors.initials: J
authors.lastname: Yoshimura
mesh_terms: D017209:Apoptosis; D003470:Culture Media; D012441:Saccharomyces cerevisiae / Q000166:cytology*
chemical_list: D003470:Culture Media