Abstract
The validity of the assumption that the specific growth rate of coccoid microorganisms can be expressed as the absolute value of the derivative of frequency of dividing cells (FDC) with respect to time was tested experimentally using a Microcystis aeruginosa strain. FDC was calculated based on the assumption that elongated cells, constricted cells or both may correspond to dividing cells. The specific growth rates that were calculated from the diel changes in FDC were compared with those calculated from the change in the cell density. The results revealed that constricted cells can serve as the optimal dividing cells, and the calculated specific growth rates were statistically identical to those obtained by the change in the cell density.
