Recent posting suggested that 1 OD unit of S.cerevisiae was equivalent
to 50x10^6 cfu. Having worked with the strain HF7c for a couple of years now, I
can safely say that the faster tha yeast are growing, the more there are per
OD600 unit: from 1x10^7 with a stationary culture, up to 3-5x10^7 for a log
growth phase culture. Careful observation will reveal that the number of cells
per OD600 unit does not increase smoothly - even when in log phase, the cell:OD
unit ratio tends to fluctuate, probably due to the asymmetric division of the
cells, combined with the extended G1 of the daughter cell population.
In short, the number of cells per OD600 unit varies: 1-5x10^7 is a
ballpark estimate. I usually assume 3x10^7 in log growth cultures. This ratio
may also vary between strains to some extent . . . long live empiricism!