Bacterial Growth and Its Phases

Bacterial growth is defined as the division of bacteria producing two identical cells. This process is called binary division and doubles the number of bacteria. All three cells are identical. Bacteria experience a sudden increase in growth to allow them to survive and grow. In order to show the growth curve of bacteria, scientists have created a perfect habitat for predicting bacterial growth curves. Growth curves allow scientists to understand how specific bacteria function and how they inhibit their growth.

The growth phase of bacterial cells is described in growth curves consisting of lag phase, log phase, stationary phase and death phase (Zwietering et al., 1990). During the lag phase, bacterial cells begin to grow for some time due to the new environment. The time interval of the lag phase depends on the growth conditions and the history of the inoculum. If the grown cultures are transferred to the same medium under the same conditions, there is no retardation period and the exponential growth phase begins immediately. However, a delay period was observed when the transferred inoculum was taken from the stationary phase of the old culture. This is because some of the cell's key points are exhausted and it takes time to biosynthesize new components. A delay period was also observed when the cells were transferred from rich medium to poor medium. Therefore, the cells need time to produce new enzymes. Therefore growth is hindered

In the lag phase, the bacteria adapt to the growth conditions. This is the period in which individual bacteria mature, but are not yet divided. The synthesis of RNA, enzymes and other molecules occurs during the lag phase of the bacterial growth cycle. In the lag phase, cell change is small because the cells can not be grown immediately in fresh medium. This period, with little or no cell division, is called the lag phase and may last from one hour to several days. At this stage, the cells are not dormant

Bacterial growth follows four stages. When a group of bacteria enters a very nutritious environment that allows growth for the first time, the cells need to adapt to their new environment. The first stage of growth is a lag phase, a slow growth phase for cells to adapt to the high nutrient environment and prepare for rapid growth. Late emergence has a high rate of biosynthesis due to proteins necessary for rapid growth. The second stage of growth is logarithmic phase, also called exponential phase. The log phase is characterized by rapid exponential growth. The rate of cell proliferation during this phase is called the proliferation rate (k) and the time it takes for the cells to doubled is called the production time (g). In log phase, nutrients are metabolized at maximum rate until one of the nutrients is exhausted and restricted growth. The third stage of growth is a period of time caused by exhaustion of nutrients.