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

摘要

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.