What is sporulation and when does it typically occur?

• A. The lysis of cells under stress; during log phase
• B. The reproduction of cells; during exponential phase
• C. The mechanism of biofilm formation; during stationary phase
• D. The formation of endospores in response to nutrient limitation, usually during stationary phase in certain bacteria

Answer: (D)

Sporulation is the process by which certain bacteria differentiate into dormant endospores in response to nutrient limitation. This is a survival strategy, not reproduction. It is typically triggered during stationary phase, when nutrients are scarce and growth has slowed. The endospore is highly resistant to heat, desiccation, chemicals, and radiation, allowing the organism to endure until conditions improve. Only certain bacteria form endospores—most notably Bacillus and Clostridium. The other options describe processes that are not sporulation: lysis would destroy cells, reproduction implies cell division, and biofilm formation is a community mode of growth, not endospore formation.