A theoretical equation for diauxic growth and its application to the kinetics of the early development of the sea urchin embryo.

The equation for diauxic growth is derived as a linear combination of two functions describing a slow and a fast rate of cell multiplication. The growth curve displays the typical biphasic shape, containing two sigmoidal branches. The curve fits very satisfactorily experimental data describing the increase of cell number in developing sea urchin embryos as a function of time, thus suggesting the presence of diauxia in this system. The hypothesis is formulated that diauxia in sea urchin embryos is the expression of two distinct metabolic pathways that result in a slow and a fast division process.