Procedure

• 1. After 12 hours, aseptically remove 0.1 ml from each of the three cultures, add 0.1 ml of trypan blue and count the total number of cells and the number of blue cells. Compute the number of viable cells/ml.

      

  2. After 24 hours (from the time of seeding), repeat step 1.

      

  3. Continue to repeat step 1 at 24 hour periods (i.e. daily) until there is no change in the number of cells/ml of culture.

      

  4. Plot cell concentration on a log scale vs time of culture. Identify and label the Lag, Log and Plateau phases for your culture.

      

  5. Select a period of time during the Log Phase and compute the doubling time for your culture. That is, the time required during the Log Phase to exactly double the number of cells/ml.