Conclusions
While spectrophotometry is widely used to assess the growth and fitness
of microbial cultures, it has important limitations. Flow cytometry is a
more accurate method for measuring population size but it is not as
widely available or as cost-effective as spectrophotometry. Our work
shows that the relationship between cell density (from
spectrophotometry) and cell count data (from flow cytometry) differs
among Saccharomyces yeast species. Thus, when conducting research
on non-model strains and species of yeast and flow cytometry is not
available, we caution to calibrate cell density measurements carefully
(e.g. by manual cell or colony counting) prior to comparative fitness
analysis, and to take in account the diverse ecology, life history, and
physical properties of yeast species to avoid biological
misinterpretations.