Following my question, I got the following responses:
John R. Rebers (jrebers at nmu.edu, Northern Michigan University): The
measurement is based on light scattering by the bacteria, rather than
light absorption, so I suspect the A620 measurement would come pretty
Nico.Mertens at lmbl.rug.ac.be (Flemish Institute of Biotechnology): Some
people also measure densities at 650, so I would use 620nm......
They both mentioned that standardisation is required.
Thanks very much.
University of British Columbia
achang at hivnet.ubc.ca