The iron superoxide dismutase from the filamentous cyanobacterium Nostoc PCC 7120. Localization, overexpression, and biochemical characterization.

The nitrogen-fixing filamentous cyanobacterium Nostoc PCC 7120 (formerly named Anabaena PCC 7120) possesses two genes for superoxide dismutase, a unique membrane-associated manganese superoxide dismutase (MnSOD) and a soluble iron superoxide dismutase (FeSOD). A phylogenetic analysis of FeSODs shows that cyanobacterial enzymes form a well separated cluster with filamentous species found in one subcluster and unicellular species in the other. Activity staining, inhibition patterns, and immunogold labeling show that FeSOD is localized in the cytosol of vegetative cells and heterocysts (nitrogenase containing specialized cells formed during nitrogen-limiting conditions).

Superoxide dismutase activity in the cyanobacterium Microcystis aeruginosa after surface bloom formation.

•  The presence of superoxide dismutase (SOD) enzymes and the response of SOD after in vitro induction and decay of a surface bloom are shown in cultures of the cyanobacterium Microcystis aeruginosa. •  The SOD enzymes of surface blooms, early degenerate and completely degenerate cultures were assayed by staining for SOD activity, immunoblotting and immunogold labelling. •  One band of Mn- and three bands of Fe-SOD were detected in cell extracts.

Immunocytochemical localization of Fe-SOD in different cells of Anabaena cylindrica Lemm. grown at two different photon irradiances.

Superoxide dismutase (SOD) converts superoxide radicals into hydrogen peroxide and molecular oxygen and therefore represents the primary defence against oxygen damage. Using antibodies against Anabaena cylindrica Lemm. iron-SOD, the isoenzyme was localized by immunogold labelling in vegetative cells, heterocysts and akinetes of the cyanobacterium Anabaena cylindrica grown at different light intensities.