Calcium uptake kinetics in relation to conidiation in submerged cultures of Penicillium cyclopium

Abstract

Uptake of calcium ions by Penicillium cyclopium in submerged culture was biphasic. The ion underwent rapid initial binding to the mycelium with a dissociation constant (KD) value of 0.114 mM-Ca2+ and binding capacity (Yt) of 3.5 nmol-Ca2+ (mg dry wt)−1. Metabolismindependent chemical adsorption of calcium was followed by metabolism-dependent active transport with a Km value of 1.88 m m and Vmax of 8.9 nmol-Ca2+ (mg dry wt)−1 min−1. Time-course experiments showed that exposures of mycelium to Ca2+ for periods as brief as 30 s were accompanied by substantial Ca2+ binding, but negligible active transport of the ion, and resulted in conidiation identical to that in cultures continuously exposed to Ca2+. The relationships between calcium binding and the mechanisms of conidiation in P. cyclopium are discussed.