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CFU/ml Calculation Formula:
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OD600 to CFU conversion is a method used in microbiology to estimate the number of colony forming units (CFU) per milliliter based on optical density measurements at 600nm wavelength. This conversion requires a calibration factor specific to the microorganism and growth conditions.
The calculator uses the simple conversion formula:
Where:
Explanation: The calibration factor is specific to each bacterial strain and must be determined experimentally by creating a standard curve comparing OD600 measurements with actual CFU counts.
Details: Accurate CFU estimation is crucial for microbial growth studies, fermentation processes, antibiotic susceptibility testing, and various biomedical research applications where precise cell concentration is required.
Tips: Enter the OD600 value and the appropriate calibration factor for your specific microorganism. Ensure both values are positive numbers for accurate calculation.
Q1: How do I determine the calibration factor?
A: The calibration factor is determined experimentally by measuring OD600 and performing serial dilutions followed by plate counting to obtain actual CFU counts for several samples.
Q2: Is the calibration factor constant for all bacteria?
A: No, the calibration factor varies between different bacterial species, strains, and even growth conditions. Each requires its own specific calibration.
Q3: What is the typical range for calibration factors?
A: Calibration factors typically range from 1×10^8 to 1×10^9 CFU/OD unit, depending on the bacterial size and growth characteristics.
Q4: When is OD600 measurement not accurate for CFU estimation?
A: OD600 may not be accurate during late stationary phase, with filamentous bacteria, or when cells form clumps or biofilms.
Q5: Can I use this calculator for yeast or other microorganisms?
A: Yes, but you must determine the appropriate calibration factor specifically for the microorganism you are working with.