yeast cell counts

[Suzanne Schulz]

We are have a basic question about yeast cell counts.  I have been
reading the A600 of yeast cultures to determine approximate cell
numbers. I usually dilute the cells 1:10 to keep the absorbance between
0.1 and 1.0 as I assumed this was a linear function.  I recently noticed
that a 1:20 dilution gave an A600 of 1.0 so this = 20 OD/ml. But the
same culture diluted 1:40 had an A600 = .65, so multiply x 40 = 26
OD/ml. The more I dilute the culture and more cells I have. How can I
accurately compare culture densities??

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