The phase in which inoculum is added to fresh culture medium and cells do not increase in number but become metabolically active and enlarge is called:

• A. Lag phase
• B. Log phase
• C. Death phase
• D. Persister cells

Answer: (A)

After inoculation into fresh medium, microbes enter a lag phase. During this time they are metabolically active, synthesizing enzymes, repairing damage, and adjusting to the new environment, but cell division is temporarily paused, so the population size doesn’t rise. This preparation period ends when cells are ready to replicate, leading into rapid growth.

This isn’t the exponential (log) phase, where numbers actually increase quickly due to binary fission; nor is it the death phase, where the population declines. Persister cells are dormant variants that survive stress and aren’t a growth-phase description of the initial inoculation period.