Pseudomonas putida, a saprophytic root-colonizing bacterium, produces multiple forms of catalase. Catalase A, which increases in specific activity during growth phase and after treatment with H 2 O 2 , is located in the cytoplasm and is inhibited by 3-amino-1,2,4-triazole, EDTA, and cyanide, but not by chloroform–methanol treatment. Catalase B, which is induced by external H 2 O 2 or during stationary phase of growth, is membrane associated and is inhibited by chloroform–methanol, EDTA, and cyanide, but not by aminotriazole. Catalase A has a broad pH optimum, from pH 6.0 to 11.0, with two peaks, at pH 8.0 and 11.0. Catalase B is most active at pH 5.0–11.0. Mutant J-1, generated by ethyl methanesulfonate mutagenesis, lacked catalase A activity in extracts of cells harvested throughout lag to early stationary growth phase in liquid medium. Catalase B was produced by J-1 in stationary phase. Exposure of J-1 to H 2 O 2 caused the production of both catalase A and catalase B. Mutant J-1 was more susceptible to cell death than the wild type upon direct exposure to 2.5 mM H 2 O 2 but survived this treatment after exposure to lower (0.3 mM), nonlethal doses of H 2 O 2 . The ability to adapt to H 2 O 2 may be related to the behaviour of J-1 on roots where active oxygen species are produced by root surface enzymes. J-1 colonized root surfaces at wild-type levels and produced catalases A and B after exposure to root surfaces for 12 h.
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Katsuwon et al. (1992) studied this question.