After a period of rapid growth (log phase), bacterial growth rates will slow and enter the stationary phase. The number of viable cells no longer increases, but instead stays constant. In this activity you will indicate the statements that correctly describe what is happening during stationary phase. Reasons?

A. The number of cells that are dying is balanced by the number of new cells that are being formed.

B. Cells are not increasing in number because they have not yet adjusted to the nutrient availability in the new media.

C. Harmful waste products may be accumulating.

D. The cells are likely running out of nutrients.

A. The number of cells that are dying is balanced by the number of new cells that are being formed.

C. Harmful waste products may be accumulating.

D. The cells are likely running out of nutrients.

Explanation:

During the stationary phase, the number of viable cells remains constant. This may be due to a balance between cell division and cell death wherein the total number of newly formed cells and the cells undergoing death are equal.

Nutrient limitation is one of the several factors that make the microbial cells to enter the stationary phase. Depletion of nutrients slows down the population growth.

Accumulation of toxic waste products as it occurs during the growth of anaerobic bacteria also adversely affects the population growth.

For example, the accumulation of lactic acid and other organic acids (by-products of anaerobic respiration) inhibits the growth of the population by making the medium acidic.