question on CFU - (Feb/15/2005 )

In the publications, people always like to describe the bacteria suspension have a CFU 10 to the power 8 etc. I just wonder how they can know the exact CFU reading, or how we can estimate the CFU reading?

It is so appreciate, if someone know it.

Thank u very much.

usually you have to correlate a specific ODx with so and so much CFUs by one way or the other. commonly used is the method, where you get you OD to a fixed value (like 0.5) and do some serial plating in triplicates with that dillution. once counted, you should get some idea, how many CFUs are there in a given volume of culture with a given OD.

Example : Your OD600nm=0.5, the plating shows that 5.2E6 CFUs/100µl are there, you can conclude, that 1ml of an OD600nm=0.5 culture (for the tested organism) equals 5.2E7 CFU. (5.2E6/100µl*10= 5.2E7/ml)

mike

:)thx a lot.