0.6667
hours
40
minutes
6
64
1.5
gen/hour
0.6667
hours
40
minutes
6
64
1.5
gen/hour
The Generation Time Calculator computes how long it takes for a microbial population to double during exponential growth. Generation time (also called doubling time) is a defining characteristic of each bacterial species and is affected by growth conditions including temperature, nutrients, and oxygen availability.
Provide the initial and final cell counts along with the time elapsed to determine the generation time and the number of generations that occurred.
Generation time (g) is calculated from the exponential growth equation:
g = t × ln(2) / ln(Nt / N₀)
This can also be written as:
g = t × log(2) / log(Nt / N₀)
Both forms are equivalent since the log base cancels out. The number of generations (n) that occurred in the time period is: n = log₂(Nt / N₀).
Inputs
Results
Starting with 5,000 cells and reaching 320,000 in 2 hours means 6 generations occurred with a generation time of exactly 20 minutes per doubling.
Inputs
Results
M. tuberculosis is notoriously slow-growing, with a generation time of about 24 hours. In 48 hours, only 2 doublings occurred.
They are the same concept. Generation time refers specifically to the time for a microorganism to complete one round of cell division, which results in the population doubling. The terms are used interchangeably in microbiology textbooks.
The fastest known doubling time is about 4.8 minutes for Vibrio natriegens. E. coli doubles in about 20 minutes under optimal conditions. On the slow end, Mycobacterium tuberculosis takes 15-24 hours, and some deep-sea organisms may take weeks to months to divide once.
Measurements must be taken during exponential (log) phase growth only. Take multiple time points and plot log(cell count) versus time. The linear portion of this plot represents true exponential growth. Measure the slope from this linear region to calculate growth rate and generation time.
Roboculator Team
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