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The catalase and superoxide dismutase genes are transcriptionally up-regulated upon oxidative stress in the strictly anaerobic archaeon Methanosarcina barkeri

¹ Department of Microbiology, Biological Faculty, Lomonosov Moscow State University, Vorob'evy Hills 1/12, 119992 Moscow, Russia
² Department of Environmental Toxicology, Swiss Federal Institute of Aquatic Science and Technology (EAWAG), Überlandstrasse 133, 8600 Dübendorf, Switzerland

Correspondence
Andrei L. Brioukhanov
brjuchanov{at}mail.ru

Methanosarcina barkeri is a strictly anaerobic methanogenic archaeon, which can survive oxidative stress. The oxidative stress agent paraquat (PQ) suppressed growth of M. barkeri at concentrations of 50–200 µM. Hydrogen peroxide (H₂O₂) inhibited growth at concentrations of 0.4–1.6 mM. Catalase activity in cell-free extracts of M. barkeri increased about threefold during H₂O₂ stress (1.3 mM H₂O₂, 2–4 h exposure) and nearly twofold during superoxide stress (160 µM PQ, 2 h exposure). PQ (160 µM, 2–4 h exposure) and H₂O₂ (1.3 mM, 2 h exposure) also influenced superoxide dismutase activity in cell-free extracts of M. barkeri. Dot-blot analysis was performed on total RNA isolated from H₂O₂- and PQ-exposed cultures, using labelled internal DNA fragments of the sod and kat genes. It was shown that H₂O₂ but not PQ strongly induced up-regulation of the kat gene. PQ and to a lesser degree H₂O₂ induced the expression of superoxide dismutase. The results indicate the regulation of the adaptive response of M. barkeri to different oxidative stresses.