Final answer:
The generation or doubling time of a bacterium is the period it takes for the population to double in size through binary fission. It varies across species and environmental conditions, with some bacteria like E. coli doubling very quickly, while others like M. tuberculosis take much longer.
Step-by-step explanation:
Generation Time in Bacteria
The generation time, or doubling time, of a bacterium is defined as the time it takes for a bacterial population to double in number through one round of binary fission. This time period can vary significantly depending on the species and environmental conditions. For instance, Escherichia coli can double every 20 minutes under optimal laboratory conditions, while Mycobacterium tuberculosis has a doubling time of 15 to 20 hours. Moreover, in harsh environments, even E. coli can take several days to double.
Bacteria typically go through four phases of growth in a closed system: the lag phase, the logarithmic or exponential phase, the stationary phase, and the death phase. During the exponential phase, bacteria exhibit exponential growth where the doubling time remains constant. A variety of methods including viable cell count, pour plate, spread plate, membrane filtration, the most probable number (MPN) method, and indirect measurement of turbidity or metabolic activity can be used to estimate the number of viable cells and thus determine the doubling time in bacterial cultures.
Understanding the concept of doubling time is essential for fields such as microbiology, biotechnology, and medicine, where controlling or predicting bacterial growth is vital. A common example of exponential growth involving bacteria is illustrated in an experiment where bacteria in a jar double every 10 minutes. This type of growth produces a J-shaped curve when plotted over time, indicating the accelerating growth rate of a bacterial population during the exponential phase.