Which phase of the microbial growth curve in a closed broth culture is characterized by rapid cell division and exponential increase in cell number?

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

Answer: (D)

Verified step by step guidance

1. Understand the microbial growth curve phases: Lag phase, Log (exponential) phase, Stationary phase, and Death phase.
2. Identify the characteristics of each phase: Lag phase involves adaptation with little to no cell division; Log phase involves rapid cell division and exponential increase in cell number; Stationary phase is when growth rate slows and stabilizes due to nutrient depletion; Death phase is when cells die at an exponential rate.
3. Focus on the phase where cells are actively dividing and the population size increases exponentially, which is the Log (exponential) phase.
4. Recall that during the Log phase, cells are metabolically active and dividing at their maximum rate, leading to a steep upward slope in the growth curve.
5. Conclude that the phase characterized by rapid cell division and exponential increase in cell number is the Log (exponential) phase.