出芽酵母の培養とメンテナンス

The yeast growth curve has three major phases. During lag phase, cells acclimate to the environment and grow in size but do not divide. In log phase, cells actively divide, leading to cell doubling. Once nutrients deplete, cells enter stationary phase, where division slows and the population remains constant.

Optical density, or OD, measures the logarithmic ratio of light intensity entering a yeast suspension to light passing through it. A spectrophotometer measures OD at 600 nm wavelength. Plotting OD values over time generates a growth curve that tracks population changes and helps determine cell viability and doubling time.

Rich yeast growth media contains three major components: yeast extract, which provides amino acids, vitamins, and carbohydrates; peptone, the primary amino acid source derived from animal meat or milk; and glucose, a sugar source providing energy. After dissolving these in water, the mixture is sterilized using an autoclave before use.

Streak yeast cells onto an agar plate using a sterile instrument to spread the culture. Individual colonies form around the streaks, each derived from a single cell. Pick one colony and inoculate it into growth media by mixing briefly. Incubate at 30°C in a shaker for 48 hours to establish a pure culture.

Doubling time is the period required for a yeast cell population to double in number, calculated using OD measurements from log phase. Wild-type yeast typically has a doubling time of approximately 90 minutes. Knowing doubling time allows researchers to plan experiments throughout the day and predict when cultures reach desired cell densities.

Yeast grown on plates can be stored at 4°C for up to three months, though re-streaking on fresh plates is recommended before inoculating new cultures. For long-term storage, aliquot cells in cryovials containing glycerol and store at -80°C, where they remain viable for several years.

Stationary phase yeast cells study genes regulating genomic DNA instability during aging by plating on selective media where only mutated cells form colonies. Chronological aging studies analyze cell viability loss over time using liquid cultures and growth curves. Log phase cells, representing healthy normal cells, are used to study eukaryotic organelles like ribosomes through reproduction of saccharomyces cerevisiae sexual and asexual processes.