Medium-induced changes in patterns of free and combined amino acids in mycelium of Serpula lacrimans

Abstract

Mycelium grown on medium containing either 7·5 or 0·075 m m ammonium sulphate as sole nitrogen source was separated into soluble and insoluble fractions and the amino acid compositions of extracts and hydrolysed residues were determined. Mycelial strands grown from wood were also analysed. Glutamic acid, and possibly glutamine and pyroglutamate, were found to be the most abundant free amino acids, and, together with ornithine, were most affected by the abundance of nitrogen in the medium. The total amino acid content of the hydrolysed residues also varied with the medium but no single amino acid showed a disproportionate change in amount. The amino acid composition of mycelial strands was very similar to that of the mycelium on a low-nitrogen medium. It was concluded that nitrogen can be stored in the form of free amino acid in the mycelium, and that the amino acids most likely to act as such stores are glutamic acid, possibly with glutamine and pyroglutamic acid, and ornithine.