Susceptibility to Hydrogen Peroxide and Catalase Activity of Root Nodule Bacteria

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  The root nodule bacteria (free-living cells) tested had higher susceptibility to hydrogen peroxide (H₂O₂) than the other genera of aerobic or facultative anaerobic bacteria tested. The catalase activities tended to have a positive correlation with H₂O₂ resistance among all bacteria tested. Addition of a catalase inhibitor such as 3-amino-1, 2, 4-triazole increased the susceptibility to H₂O₂. These results suggest that the lower catalase activity brings about the higher susceptibility of root nodule bacteria to H₂O₂. Root nodule bacteria seemed to have two or three catalase isozymes during growth and their catalase activities were higher in log phase than in stationary phase, contrary to other genera of bacteria tested.