I am working with Cohnella xylanilytica DSM 25239 and I want an accurate and reproducible way to count the CFU. Using spectroscopy, if I adjust the OD600 to between 0.08-0.1 , can I safely assume that the CFU count is ~1.5 x 10^8 ,as you would with E . Coli ATCC 25299, or is there a large variation in CFU count between different bacteria in this OD range?
Following the procedure on page 12 of the attached link.
https://webcache.googleusercontent.com/search?q=cache:EuKi09Qna0sJ:https://www.researchgate.net/file.PostFileLoader.html%3Fid%3D56466b465f7f71946b8b45f2%26assetKey%3DAS%253A295464181223441%25401447455558839+&cd=1&hl=en&ct=clnk&gl=ca
Nope you cannot do this (especially never at decimal places) without your own strain specific calibration graph. The plate counting method is still the most accurate one. If you want to avoid culturing time and calibration graphs, use the microscopy-counting chamber. It has an acceptable accuracy for most cases.
You really need to generate a standard curve with your specific strain, at least one time. There is notable variation between OD and CFU with different bacteria.
Dear Logan, McFarland standart vary on the basis of size of microorganisms. The McFarland values give cells/ml concentration. The attachmet can help you related to McFarland standart.
Best regards.
- Badges
- Science topic
- Similar topics
- Biological Science
- Microbiology
- Microorganisms
- Bacteria