Simple, fast and accurate method for the determination of glycogen in the model unicellular cyanobacterium Synechocystis sp. PCC 6803

Glycogen is a highly soluble branched polymer composed of glucose monomers linked by glycosidic bonds that represents, together with starch, one of the main energy storage compounds in living organisms. While starch is present in plant cells, glycogen is present in bacteria, protozoa, fungi and animal cells. Due to its essential function, it has been the subject of intense research for almost two centuries. Different procedures for the isolation and quantification of glycogen, according to the origin of the sample and/or the purpose of the study, have been reported in the literature. The objective of this study is to optimize the methodology for the determination of glycogen in cyanobacteria, as the interest in cyanobacterial glycogen has increased in recent years due to the biotechnological application of these microorganisms. In the present work, the methodology reported for the quantification of glycogen in cyanobacteria has been reviewed and an extensive empirical analysis has been performed showing how this methodology can be optimized significantly to reduce time and improve reliability and reproducibility. Based on these results, a simple and fast protocol for quantification of glycogen in the model unicellular cyanobacterium Synechocystis sp. PCC 6803 is presented, which could also be successfully adapted to other cyanobacteria.

Dismutation of hydroxylamine to ammonia and nitrite by a novel, membrane-bound enzyme from the cyanobacterium Phormidium uncinatum

Extracts from ammonium-grown phototrophic cultures of Phormidium uncinatum exhibited a catalytic and stoichiometric formation of nitrite and ammonia from hydrogen peroxide and hydroxylamine. This reaction was due to a novel enzyme (referred to as hydroxylamine dismutase), which was bound to the heavier thylakoid membranes. The enzyme was solubilized from the membranes by detergent treatment and further purified by ion-exchange chromatography. On the basis of inhibitor studies, the involvement of metal ions and sulfhydryl groups in the characteristic reaction is suggested.