Certified Professional Food Safety (CP-FS) Practice Exam

During which phase do bacteria reach their equilibrium in numbers?

1. Lag Phase

2. Log Phase

3. Stationary Phase

4. Death Phase

The correct answer is: Stationary Phase

The correct answer is the Stationary Phase. During this phase, the growth rate of bacteria slows down and stabilizes as the number of viable cells remains constant over time. This equilibrium is reached due to the exhaustion of nutrients and the accumulation of waste products, which ultimately leads to a balance between the number of cells dividing and those dying. In the Lag Phase, bacteria are adapting to their environment and are not yet multiplying at a significant rate, so growth has not yet stabilized. During the Log Phase, abundant resources lead to rapid cell division, and the population increases exponentially, but it is not yet in equilibrium. In the Death Phase, the number of viable cells decreases as environmental conditions continue to deteriorate, leading to a decline in population rather than an equilibrium in numbers. Hence, the Stationary Phase is unique for its characteristic balance between the proliferation and death of bacterial cells.