Death phase: As the limiting factors intensity, cells begin to die at exponential rate (literally perishing in their own wastes) and most are unable to multiply. The exhaustion of nutrients, accumulation of waste products and harmful changes in pH may all play a role.Ĥ. What causes exponential growth to stop is not always clear. The curve levels off because the rate of cell death balances out the rate of multiplication. In this phase, the population enters a survival mode in which cells stop growing or grow slowly. This period of equilibrium is called stationary phase. Stationary phase: The number of microbial death balances the number of new cells and population stabilizes. The log phase is the time when cells are most active metabolically and is preferred for industrial purposes.ģ. During this phase, the population fulfills its potential generation time and growth is balanced and genetically coordinated. This phase will continue as long as cells have adequate nutrients and the environment is favorable. Because the generation time is constant, a logarithmic plot of growth during log phase is a straight line. Cellular reproduction is most active during this period and generation time reaches a constant minimum. It is a period during which the curve increases geometrically. Log phase: Eventually, the cells begin to divide and enter a period of growth or logarithmic increase, called the log/ exponential growth phase. Physiologically they are very active and are synthesizing new protoplasm.Ģ. The microbial population is undergoing a period of intense metabolic activity involving in particular, synthesis of enzymes and various molecules. During this time, however, the cells are not dormant. This period of little or no cell division is called the lag phase. Some cells may die from the shock of transfer or the inability to adapt to the new environment. Lag phase: In a fresh medium after few cells are inoculated, for a while number of cells changes very little because the cells do not immediately reproduce. #1 Top ranking article submission websiteġ. Get Envato Elements, Prime Video, Hotstar and Netflix For Free For showing the growth curve logarithmic scales are generally used.īest safe and secure cloud storage with password protection It is difficult to show changes in population by using arithmetic numbers. When a few bacteria are inoculated into a liquid growth medium and population is counted at intervals, it is possible to plot a bacterial growth curve showing growth of cells over time. Growth rate, R=1/g= t/n Bacterial growth curve It is the alternative value of generation time. Growth rate depends on generation time “g”. The rate of bacterial multiplication per hour is called the growth rate (R). The generation time “g” can be determined from the number of generations “n” that occur in a particular time interval “t”. Generation time depends on nutrient media, pH, temperature etc. For bacteria it is the time, required for a complete fission cycle. The time required for a cell to divide or a population to divide is known as the generation time.
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