During which phase of the microbial growth curve in a closed system are bacteria most susceptible to antibiotics?

• A. Log (exponential) phase
• B. Lag phase
• C. Death (decline) phase
• D. Stationary phase

Answer: (A)

Verified step by step guidance

1. Understand the microbial growth curve phases: Lag phase (adaptation period), Log (exponential) phase (rapid cell division), Stationary phase (growth rate equals death rate), and Death (decline) phase (cells dying).
2. Recognize that antibiotics typically target processes involved in active cell growth and division, such as cell wall synthesis or protein production.
3. Identify that during the Log (exponential) phase, bacteria are metabolically active and dividing rapidly, making them more vulnerable to antibiotics that disrupt these processes.
4. Contrast this with the Lag phase, where bacteria are metabolically active but not dividing yet, and the Stationary and Death phases, where growth slows or cells die, reducing antibiotic effectiveness.
5. Conclude that bacteria are most susceptible to antibiotics during the Log (exponential) phase because this is when their cellular activities targeted by antibiotics are at their peak.