In a closed system, spores are formed during which of the following phases of bacterial growth?

Spore formation usually occurs during the stationary phase, when cell growth ceases because of a developing lack of nutrients or accumulation of toxins. The exponential phase and log phase are descriptors for the steady state of active growth occurring after the lag phase and before the stationary phase. Many antibiotics are most effective in this period. The lag phase is the initial period of adaptation, prior to growth, which occurs when organisms are introduced to a new environment. Ref: Ray C.G., Ryan K.J. (2010). Chapter 21. The Nature of Bacteria. In C.G. Ray, K.J. Ryan (Eds), Sherris Medical Microbiology, 5e.