Endogenous reserves and survival of blastospores of Beauveria bassiana harvested from carbon- and nitrogen-limited batch cultures

Abstract

Beauveria bassiana was grown in submerged culture on modified Vogel's medium. Patterns of utilization of glucose and ammonium, and analysis of the elemental composition of stationary phase biomass showed that cultures initially containing 3·3 g (NH4)2SO4l−1 and 10 g glucose l−1 were carbon-limited, whilst cultures containing 0·8 g (NH4)2SO4l−1 and 10 g glucose l−1 were nitrogen-limited. Modal volume, wall thickness and endogenous reserves (total carbohydrate, glycogen and lipid) of blastospores harvested from the stationary phase of nitrogen-limited cultures were all greater than values observed for those from carbon-limited cultures. The longevity (ability to form germ tubes) of conidia and carbon-limited blastospores stored in quarter strength Ringer's solution was determined at 4°, 25° and 30 °C, and for both spore types, was inversely related to temperature. At any given temperature, conidia survived longer than blastospores, but at 25°, nitrogen-limited blastospores survived longer than carbon-limited blastospores. Endogenous reserves of blastospores from carbon- and nitrogen-limited cultures declined during storage at 25°, and were related biphasically to spore longevity.