The growth of bacterial populations occurs in several stages β termed lag, log, stationary and death. During the lag phase, active metabolic activity occurs, but no growth. During the log phase, metabolic activity is increased and most intense and cell production is at its highest level.
Following this phase, the growth rate slows and the production of new cells equals the rate of cell death. This is known as the stationary phase and involves the establishment of an equilibrium in population numbers and a slowing of the metabolic activities of individual cells.
The stationary phase reflects a change in growing rate β for example, a lack of nutrients and/or accumulation of waste products. When the number of cell deaths exceeds the number of new cells formed and the population shifts to a net reduction in numbers, the population enters the death phase or logarithmic decline phase. The population may diminish until only a few cells remain, or the population may die out entirely.