Unfortunately you will have to do the experiment of making plate counts
at different OD 600s and setting up a standard curve. This is a lot of
work but there is no way around it as far as I know. If anybody out
there knows differently I would love to hear from her/him.
We have found that with Rhizobium you can't even extrapolate from one
strain to another as things like EPS production can result in 10-fold
differences in cfu at the same OD. I believe this fact is also mentioned
in Sambrook et al. re; E. coli strains.
Then every time you change medium you have to set up a new calibration.
MH
