Disruption of a glycogen-branching enzyme gene, glgB, specifically affects the sporulation-associated phase of glycogen accumulation in Streptomyces aureofaciens.

In the course of differentiation, glycogen is accumulated in two discrete phases: in substrate hyphae that undergo aerial mycelium formation (phase I), and during septation of aerial hyphae (phase II). We have disrupted a previously identified gene, , encoding a putative glycogen-branching enzyme in . Disruption of the gene had no profound effect on sporulation. However, the amount of glycogen-like polysaccharides, compared to wild-type (WT) , decreased in the late stage of differentiation of the -disrupted strain. Absorption spectra of polysaccharides extracted from the WT and -disrupted strains have shown the presence of glycogen in both strains in the first stage of differentiation (aerial mycelium formation), and unbranched glucan was detected in the -disrupted strain in the late stage of differentiation. The results were confirmed by electron microscopy after silver proteinate staining of glycogen granules. Two distinct glycogen-branching enzymes, which had temporally different expression during differentiation, were detected in WT . The absence of this enzyme activity in the late stage of differentiation in the mutant suggests that the product of the gene is responsible for phase II glycogen accumulation.