Lag Phase

• A culture of bacteria begins in lag phase. During this time, bacteria acquire nutrients from the growth medium but have not started to multiply.
  
  

Log Phase

• In log phase, the bacteria have started to multiply, and multiply at their maximum rate. On an individual level, some cells still die, but many more get produced than die.
  
  

Stationary Phase

• In stationary phase, cells die at the same approximate rate that they get produced. Cells do not stop being produced in stationary phase.
  
  

Death Phase

• In death phase, cells die at a greater rate than production. Even with a name like death phase, bacterial cells still divide and produce new cells, but the death of other cells greatly overshadows any new cell production.
  
  

Effects on Bacterial Growth

• Many different types of pressure on a culture of bacterial cells can cause retardation of growth. Temperature, pH or osmotic balance that fails to reach optimal level for the specific bacteria can result in extended lag phase, or a very short log phase of growth.