Morphogenesis and free amino acid composition of the ascomyceteSphaerostilbe repensas influenced by nitrogen and calcium

Abstract

Sphaerostilbe repens utilizes nitrate and ammonium as nitrogen sources. Differentiation of mycelium into rhizomorphs and coremia was reduced in the presence of nitrate and completely inhibited in the absence of calcium. The most abundant free amino acids were, in decreasing order: alanine, glutamine, glutatomic acid, serine, aspartic acid, γ‐aminobutyric acid, arginine and threonine. These compounds represented 90% of the total amino acid pool. The free amino acid composition did not vary with cultural conditions although concentrations of individual amino acids differed. In ammonium‐grown cells, γ‐aminobutyric acid increased in concentration and glutamate, aspartate and alanine decreased. Calcium‐deficient media reduced amino acid concentrations, especially of arginine and ornithine. Amino acid contents increased during the growth period and were higher in rhizomorphs than in vegetative mycelia.