Before bacteria grow, it must be supplied with the proper environment and circumstances. Temperature, concentration of oxygen, presence of water, available minerals and acidity all effect bacterial growth. Some bacteria, such as Thermophiles, require extremely high temperatures for growth, such as those in a hot spring. Conversely, Psychrophile bacteria require extremely low arctic temperatures for growth. Each type of bacteria has unique needs for initial growth that may prove inhospitable for other types of bacteria.
Bacteria in the lag phase acclimate itself to its current environment before beginning to grow. While bacteria metabolize during this phase, it does not grow quickly. Instead, it begins replicating DNA in accordance with available mineral supplies and environmental factors.
The log phase is the period of rapid growth for bacteria. Some bacteria can replicate its DNA as quickly as every 15 minutes, while others take weeks to begin maturity. A bacteria's generation time is the period it takes a bacteria to double in size. This occurs as a bacterium separates, creating two identical copies of itself called daughter cells.
In the stationary phase, bacteria slow in growth and begin to stagnate. Bacteria in this stage accumulate waste and encroach on the limit of space available to continue generation. If a bacteria is introduced into a new environment, however, it may revert back to log phase and continue with rapid growth due to newly-available nutrients and growth space.
Bacteria cease all growth during the death phase. Bacteria are unable to reproduce and may begin dying off as quickly as they grew in the log phase due to limited nutrients and growth space.