A bacterial growth curve is used to show growth of cells over time. Four basic phases of growth exist. The lag phase, the log phase, the stationary phaseand the death phase.
The Lag Phase- At first the number of cells barely changes because the process of reproduction is not immediate. This is called the lag phase because it is a a period of little or no cell division. The phase can last anywhere from an hour to several days. The cells are not dormant during this phase, however. During this the microbe is undergoing extreme metabolic activity in which enzymes and various molecules are synthesising.
The log Phase- Soon the cells begin to divide and grow or logarithmicly increase hence the name, log phase, or as it is also known, the exponential growth phase. During this period, cellular activity is occuring as the cell begins to reproduce and generation time is at a constant minimum. Because it becomes constant, the logarithmic plot of growth is a straight line. This phase is the time in which the cells are most active and production is efficient. Microorganism in this phase are particularly sensitive to adverse conditions, however, such as radiation and many antimicrobial drugs that can interfere with steps in the growth process are harm the phase.
The Stationary Phase- Growth rates slow and microbial deaths balance out withy new cells, stabalizing the population, and the metabolic activities of individual living cells also slow in a period of equilibrium called the stationary phase. The cause of the stop of exponential growth is not known. A number of possiblities exist such as exhaustion of nutrients and harmful changes in pH.
The Death Phase- Deaths eventually exceed the formation of new cells and the population enters the death phase or the logarithmic decline phrase. This phase does not stop until the population is diminished to a small fraction or the population dies out completely. Cells often undergo involution during this phrase as there morphology changes making them hard to identify. Some go through the entire phrase in days, others almost indefinitely.
The Lag Phase- At first the number of cells barely changes because the process of reproduction is not immediate. This is called the lag phase because it is a a period of little or no cell division. The phase can last anywhere from an hour to several days. The cells are not dormant during this phase, however. During this the microbe is undergoing extreme metabolic activity in which enzymes and various molecules are synthesising.
The log Phase- Soon the cells begin to divide and grow or logarithmicly increase hence the name, log phase, or as it is also known, the exponential growth phase. During this period, cellular activity is occuring as the cell begins to reproduce and generation time is at a constant minimum. Because it becomes constant, the logarithmic plot of growth is a straight line. This phase is the time in which the cells are most active and production is efficient. Microorganism in this phase are particularly sensitive to adverse conditions, however, such as radiation and many antimicrobial drugs that can interfere with steps in the growth process are harm the phase.
The Stationary Phase- Growth rates slow and microbial deaths balance out withy new cells, stabalizing the population, and the metabolic activities of individual living cells also slow in a period of equilibrium called the stationary phase. The cause of the stop of exponential growth is not known. A number of possiblities exist such as exhaustion of nutrients and harmful changes in pH.
The Death Phase- Deaths eventually exceed the formation of new cells and the population enters the death phase or the logarithmic decline phrase. This phase does not stop until the population is diminished to a small fraction or the population dies out completely. Cells often undergo involution during this phrase as there morphology changes making them hard to identify. Some go through the entire phrase in days, others almost indefinitely.