Growth curve basics — The time interval between inoculation into fresh medium and the beginning of measurable cell division is called the…

Introduction / Context:
Batch culture growth typically follows a sigmoidal curve with distinct phases: lag, exponential (log), stationary, and death (decline). Correctly identifying each phase is essential for experimental planning (induction timing), food safety (growth predictions), and bioprocess optimization (harvest points).

Given Data / Assumptions:

• Fresh inoculum is transferred into a new medium.
• There is a delay before rapid cell division begins.
• We are asked to name this initial interval.

Concept / Approach:
During the lag phase, cells adapt to their new environment. They repair damage, synthesize enzymes needed for available substrates, and adjust membrane transport systems. Although total cell number does not increase markedly, metabolic activity can be high. Once adaptation is complete, cells enter log phase, where the division rate reaches its maximum under given conditions. Later, nutrient depletion and waste accumulation bring cultures to stationary phase, followed by decline as viability decreases.

Step-by-Step Solution:

Verification / Alternative check:
Optical density and viable counts show a flat line after inoculation before rising exponentially, confirming the presence of a lag period.

Why Other Options Are Wrong:

• Log phase: occurs after lag; characterized by maximal specific growth rate.
• Stationary phase: growth equals death; occurs later.
• Decline phase: death rate exceeds growth; last phase.

Common Pitfalls:
Equating metabolic activity with population growth; cells can be active in lag without dividing.

Final Answer:
lag phase