Lag phase - A newly inoculated culture usually does not begin growing immediately but rather after of period of no growth which is referred to as the lag phase. Active cells can be used when transferred to the medium to prevent the lag phase.
Exponential or log phase - a consequence of each cell dividing to form two cells. Usually the phase with the greatest rate of increase in the population size. The rate is influenced by the environmental conditions such as temperature, aeration, and composition of medium.
Stationary phase - consider that a bacterium - a single cell - with a generation time of 20 minutes would produce a population after 48 hours. What happens to stop this?
Some factors that limit population growth - 1. intraspecific competition for nutrients which are running out as the culture ages. 2. Build up of toxic metabolites
All of this leads to a stationary phase in which the growth rate of the population is zero.
Death phase - after stationary phase the cells may remain alive for a long period of time or begin to die off as in a death phase. The cells may begin to lyse as they die and other viable cells may grow on the remains of the lysed cells in what is called cryptic growth.