Which growth phase is often optimal for producing secondary metabolites like antibiotics in some species?

• A. Lag phase
• B. Log phase
• C. Stationary phase
• D. Death phase

Answer: (C)

Secondary metabolite production, like antibiotics, typically emerges when growth slows due to nutrient limits and stress. In the stationary phase, nutrients are depleted and waste accumulates, so cells redirect energy from rapid replication toward survival and competition. This shift triggers regulatory pathways that activate secondary metabolism, leading to antibiotic synthesis as a strategy to inhibit rivals and secure scarce resources. In contrast, the lag phase is a preparatory period with little growth, the exponential (log) phase focuses on rapid biomass formation, and the death phase involves declining viability—scenarios where secondary metabolite production is not favored. Hence, the stationary phase is often the best time for producing these compounds.