Differential catalase activity and tolerance to hydrogen peroxide in the filamentous cyanobacteria Nostoc punctiforme ATCC 29133 and Anabaena sp. PCC 7120.

Photoautotrophic cyanobacteria often confront hydrogen peroxide (HO), a reactive oxygen species potentially toxic to cells when present in sufficiently high concentrations. In this study, HO tolerance ability of filamentous cyanobacteria Nostoc punctiforme ATCC 29133 (Nostoc 29133) and Anabaena sp. PCC 7120 (Anabaena 7120) was investigated at increasing concentrations of HO (0-0.5 mM). In Nostoc 29133, 0.25 and 0.5 mM HO caused a reduction in chlorophyll a content by 12 and 20%, respectively, whereas with similar treatments, a total loss of chlorophyll a was detected in Anabaena 7120. Further, Nostoc 29133 was able to maintain its photosystem II performance in the presence of HO up to a concentration of 0.5 mM, whereas in Anabaena 7120, 0.25 mM HO caused a complete reduction of photosystem II performance. The intracellular hydroperoxide level (indicator of oxidative status) did not increase to the same high level in Nostoc 29133, as compared to in Anabaena 7120 after HO treatment. This might be explained by that Nostoc 29133 showed a 20-fold higher intrinsic constitutive catalase activity than Anabaena 7120, thus indicating that the superior tolerance of Nostoc 29133 to HO stems from its higher ability to decompose HO. It is suggested that difference in HO tolerance between closely related filamentous cyanobacteria, as revealed in this study, may be taken into account for judicious selection and effective use of strains in biotechnological applications.