Streptococcus faecalis var. zymogenes was grown aerobically and anaerobically in the presence and absence of haematin, with glycerol as the carbon and energy source. Aerobic growth was stimulated by the inclusion of haematin in the medium but fumarate had no effect on growth. The bacterium was unable to grow anaerobically on glycerol unless fumarate was present; haematin had no effect on growth. NADH oxidase activity, which catalysed the oxidation of NADH + H+ to form H2O rather than H2O2, was found in the soluble fraction and was induced by aerobic growth but partially repressed when haematin was present in the medium. In contrast, a particulate NADH oxidase, which was sensitive to inhibition by antimycin A and 2-heptyl-4-hydroxyquinoline N-oxide, was induced by aerobic growth in the presence of haematin. NADH peroxidase was massively induced by aerobic growth, whereas more lactate dehydrogenase activity was found in anaerobically grown bacteria. Catalase was formed only during aerobic growth in the presence of haematin.
"Streptococcus faecalis subsp. zymogenes" was grown aerobically and anaerobically with glycerol as the source of carbon, and in the presence and absence of haematin. Catalase activity was found only during aerobic growth in the presence of haematin. The rate of appearance of catalase activity was measured on (a) addition of haematin to haematin-less aerobic cultures, and (b) aeration of haematin-containing anaerobic cultures in the presence or absence of chloramphenicol. These experiments suggested that apocatalase synthesis was induced by aeration and was not dependent on the presence of haematin in the growth medium. The binding of haem to apocatalase was oxygen dependent.
The effects of metal salts, chelating agents, and paraquat on the superoxide dismutases (SODs) ofEscherichia coli B were explored. Mn(II) increased manganese-containing SOD (MnSOD), whereas Fe(II) increased iron-containing SOD (FeSOD). Chelating agents induced MnSOD but decreased FeSOD and markedly increased the degree of induction seen with Mn(H). Paraquat also exerted a synergistic effect with Mn(II). High levels of MnSOD were achieved in the combined presence of Mn(II), chelating agent, and paraquat. All of these effects were dependent on the presence of oxygen. MnSOD, not ordinarily present in anaerobicaly grown E. coli cells, was present when the cells were grown anaerobically in the presence of chelating agents. These results are accommodated by a scheme which incorporates autogenous repression by the apoSODs and competition between Fe(H) and Mn(ll) for the metal-binding sites of the apoSODs. It is further supposed that oxygenation and intracellular O2 production favor MnSOD production because O2 oxidizes Mn(H) to Mn(III), which competes favorably with Fe(H) for the apoSODs. Escherichia coli produces two distinct homodimeric SODs. One of these contains iron (FeSOD) (25, 25a, 30), and the other contains manganese (MnSOD) (14, 26). When grown anaerobically, E. coli cells contain only FeSOD, but when grown aerobically they contain FeSOD, MnSOD, and a hybrid of these (HySOD) (9). Redox-active compounds,
Growth of Escherichia coli B in simple media enriched with Mn(II) resulted in the elevation of the manganese-containing superoxide dismutase, whereas growth in such medium enriched with iron caused increased content of the iron-containing superoxide dismutase. Enrichment of the medium with Co(II), Cu(II), Mo(VI), Zn(II), or Ni(II) had no effect. The inductions of superoxide dismutase by Mn(II) or by Fe(II) were dioxygen dependent, but these metals did not affect the CN-resistant respiration of E. coli B and did not influence the increase in the CN--resistant respiration caused by paraquat. Mn(II) and paraquat acted synergistically in elevating the superoxicde dismutase content, and Mn(II) reduced the growth inhibition imposed by paraquat. E. coli grown in the complex 3% Trypticase soy broth (BBL Microbiology Systems)-0.5% yeast extract-0.2% glucose medium contained more superoxide dismutase than did cells grown in the simple media and were less responsive to enrichment of the medium with Mn(II) or Fe(II). Nevertheless, in the presence of paraquat, inductions of superoxide dismutase by these metals could be seen even in the Trypticaseyeast eXtrpct-glucose medium. On the basis of these observations we propose that the apo-superoxide dismutases may act as autogenous repressors and that Mn(II) and Fe(II) increase the cell content of the corresponding enzymes by speeding the conversion of the apo-to the holoenzymes.Escherichia coli contains superoxide dismutases (SOD) based upon manganese (MnSOD) (17) and upon iron (FeSOD) (28). Conditions that lead to increased intracellular production of 02 have been seen to cause induction of the MnSOD, but not of the FeSOD in this organism. The conditions that have been explored include oxygenation of the medium (6-8, 10, 27), increasing growth rate in glucoselimited chemostat culture (11), shifting the metabolic emphasis from fermentable to nonfermentable substrates (12), and exposure to redox active compounds, such as paraquat (13,14), pyocyanine (15), or a variety of quinones (16). These compounds increase the cyanide-resistant respiration (13) and exhibit a toxicity that is dependent upon both dioxygen and an electron source (14), indications that their effects are mediated by 02 There was reason to suspect that metal salts, per se, might induce SOD in E. coli. Thus, Yano and Nishie observed a threefold induction of SOD in E. coli B when the growth medium was aerated, but saw a fivefold induction when an Mn(II)-enriched medium was aerated (27). Furthermore, Yamakura (27), working with Pseudomonas ovalis, noted an increase in FeSOD when the medium was enriched with iron and an increase in an electrophoretically distinct SOD, presumed to be an MnSOD, when the medium was enriched with manganese. Preliminary experiments in our laboratory, with E. coli B, showed that Mn(II) and Fe(II) did not increase CN--resistant respiration. It therefore appeared that ipductions of SOD by these metal salts, unlike the inductions by paraquat, were not mediated by increased 02 production and mig...
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