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Bacterial Growth Rate Equation:
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The bacterial growth rate (r) represents the rate at which a bacterial population increases over time. It's calculated during the exponential growth phase and is expressed as the change in population per unit time.
The calculator uses the growth rate equation:
Where:
Explanation: The equation calculates the exponential growth rate by comparing the natural log of the ratio of final to initial CFU counts over the time interval.
Details: Calculating growth rate is essential for understanding bacterial population dynamics, determining generation time, and comparing growth conditions in microbiology studies.
Tips: Enter CFU counts as whole numbers (from plate counts) and time in minutes. Ensure measurements are from the exponential growth phase for accurate results.
Q1: What is a typical bacterial growth rate?
A: Growth rates vary by species and conditions. E. coli might grow at 0.02-0.03 per minute in optimal conditions, while slower-growing bacteria might be 0.001-0.005 per minute.
Q2: How is growth rate related to doubling time?
A: Doubling time (generation time) can be calculated as \( \ln(2)/r \). A growth rate of 0.02 per minute corresponds to a doubling time of about 35 minutes.
Q3: Why use natural log (ln) instead of log10?
A: The natural log is mathematically convenient for exponential growth calculations. To convert to log10, multiply by 2.303 (ln(10)).
Q4: What if my CFU counts are from dilution plates?
A: Multiply plate counts by the dilution factor before using in the calculator to get actual CFU counts.
Q5: Can I use OD600 measurements instead of CFU?
A: OD600 can be used as a proxy for cell density, but the relationship between OD and CFU varies by growth phase and bacterial species.