Growth, nutrition, and proteolytic activity of the sap-staining fungus Ophiostoma piceae

Abstract

The sap-staining ascomycete Ophiostoma piceae strain 387N used ammonium, but not nitrate, as an inorganic nitrogen source. Organic nitrogen sources assimilated included bovine serum albumin, collagen, acid-hydrolyzed casein, urea, and various amino acids. Sucrose, glucose, maltose, raffinose, and soluble starch were suitable carbon sources. The optimum temperature for growth was near 23 °C, with an upper limit at 35 °C and minimal growth at 4 °C after 3 days. An initial pH of 6.1 yielded the greatest biomass. Proteolytic activity was greatest in cultures supplemented with protein as the nitrogen source, but some activity was detected in cultures with no assimilable source of nitrogen. Proteinases were detected throughout growth in protein-supplemented liquid media, and they appeared to hydrolyze azocoll, with optimal activity at pH 8. Isoelectric focusing gels of culture filtrates, obtained after fungal growth on protein supplemented media, showed a major proteolytic band focusing at pH 5.2. Key words: staining fungi, Ophiostoma, nutrition, biomass, proteinases.