Growth of Saprolegniaceae in Synthetic Media. II. Nitrogen Requirements and the Role of Krebs Cycle Acids

Abstract

Eleven spp. of Saprolegniaceae grow well with ammonium salts (but not nitrate salts) as sole N source if other limiting factors are absent. Fumarate, malate, succinate, or glutamate are also required for heavy growth. These acids probably act as substitutes for CO2 in maintaining the Krebs cycle of these organisms. No evidence of participation by citric or cis-aconitic acids in such a cycle in the Saprolegniaceae could be obtained. Substrates readily utilized as sources of C and energy include ethanol, glucose, starch, glycogen, and sucrose (except by Isoachlya intermedia, Protoachlya paradoxa, and Saprolegnia delica). Brevilegnia unisperma and Dictyuchus monosporus grew well only in the presence of ethanol.