Microbiology Practice Exam

What is the best description of the log phase of a bacterial growth curve?

1. Populations double under optimum conditions

2. Growth rate slows down

3. Cell death exceeds cell growth

4. Increase in nutrient consumption

The correct answer is: Populations double under optimum conditions

The log phase of a bacterial growth curve, also known as the exponential phase, is characterized by the period of rapid cell division and population growth. During this phase, bacteria are undergoing binary fission at their maximum rate, leading to an exponential increase in the number of cells. This doubling of populations occurs under optimum environmental conditions, such as adequate nutrient supply and favorable temperature. The cells are actively metabolizing, which contributes to the acceleration of growth. While there may be increased nutrient consumption as a consequence of the high metabolic activity during the log phase, the hallmark feature remains the rapid doubling of cell numbers. This distinguishes the log phase from other phases of growth; for instance, during the stationary phase, the growth rate slows as nutrient depletion and waste accumulation start to affect the population, leading to a balance where cell growth equals cell death.