Illumination is of great importance to photoautotrouphs. Transfer of Nostoc muscorum cells to dark
state resulted in an increase in PHB accumulation
(Table
3). This could possibly be due to the conversion of gly-
cogen to PHB as reported for Gloeothece PCC 6909 and
Synechocystis sp. PCC 6803 (Stal, 1992;Wu et al., 2001).