Questions: Why are bacteria most sensitive to antimicrobial medications during the exponential, or log, phase? The large accumulation of wastes is already damaging to bacteria. Bacteria are already sensitive during this phase due to a lack of nutrients. There are the greatest numbers of bacteria present during exponential phase. Many antimicrobial medications target processes most active when bacteria are growing.

The answer is the fourth one: Many antimicrobial medications target processes most active when bacteria are growing.

Explanation for each option:

1. The large accumulation of wastes is already damaging to bacteria.

   • This is incorrect. While waste accumulation can be harmful, it is more relevant during the stationary phase when growth slows down due to resource depletion and waste buildup, not during the exponential phase.

2. Bacteria are already sensitive during this phase due to a lack of nutrients.

   • This is incorrect. During the exponential phase, nutrients are typically abundant, allowing for rapid bacterial growth. Nutrient depletion is more characteristic of the stationary phase.

3. There are the greatest numbers of bacteria present during exponential phase.

   • This is incorrect. While it is true that bacterial numbers increase rapidly during the exponential phase, the sensitivity to antimicrobial medications is not directly due to the number of bacteria but rather their active growth processes.

4. Many antimicrobial medications target processes most active when bacteria are growing.

   • This is correct. Antimicrobial medications often target cellular processes such as cell wall synthesis, protein synthesis, and DNA replication, which are most active during the exponential phase when bacteria are rapidly dividing and growing.

In summary, bacteria are most sensitive to antimicrobial medications during the exponential phase because these medications target the active growth processes that are prevalent during this phase.