The life cycle of bacteria consists of four main phases: the lag phase, the exponential or log phase, the stationary phase and the death phase. Factors that trigger bacteria growth heavily rely on this life cycle. Bacteria multiply through a process known as binary fission.
During the lag phase, bacteria do not grow. They only adjust to their environment and metabolize, producing the amino acids and vitamins that they need for division. In this stage, they also make copies of DNA. If there are enough nutrients available, this phase may be very short.
In the exponential or log phase, bacteria multiply rapidly. Under favorable conditions, bacteria can double in approximately 15 minutes. However, bacteria sometimes takes days to multiply. The amount of time a culture takes to double is referred to as "generation time".
Bacteria multiply through a process known as binary fission. For a bacterium to multiply, its DNA copy drifts to two opposite sides of the membrane, creating identical daughter cells which multiply again.
The stationary stage is characterized by a decline in bacteria growth. The decline results from growth-inhibiting factors, such as the formation of inhibitory products or depletion of essential nutrients. In this phase, growth and death rates are equal. In the death phase, bacteria lose the ability to reproduce.