Cytoplasmic water-soluble β-glucans in Achlya: response to nutrient limitation

Abstract

Water-soluble β-glucans are major cytoplasmic constituents of Achlya bisexualis representing 13% (weight/weight) of mycelial dry weight. This glucan was fractionated by ion exchange into two types, a neutral form (20%) and a phosphorylated form (80%). The phosphorylated glucan contained 5% (weight/weight) phosphate when the mycelium was grown in standard medium. A 10-fold reduction in the supply of phosphate reduced the phosphate in the glucan to 1%, and a reduction in nitrogen had a similar effect. When growing mycelium was transferred to medium minus phosphate, total glucan production continued but with a reduced phosphate concentration. During starvation and calcium-induced sporulation, total glucan declined, the ratio of neutral to phosphorylated glucan remained the same, but phosphate level decreased by 49%.

Key Words:

• Achlya
• β-glucans
• neutral glucan
• phosphorylated glucan
• storage polysaccharides