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Appl Environ Microbiol. 1970 June; 19(6): 966-972
Copyright © 1970 American Society for Microbiology. All Rights Reserved.

Bacteriology of Manganese Nodules

IV. Induction of an MnO₂-Reductase System in a Marine Bacillus¹

Department of Biology, Rensselaer Polytechnic Institute, Troy, New York 12181

ABSTRACT

Bacillus 29, isolated from a ferromanganese nodule from the Atlantic Ocean, was shown to possess an MnO₂-reductase system which is induced in the presence of manganous ion. Maximal activity of the enzyme system was induced in about 5 hr in the presence of 4.35 mM MnSO₄ and was minimally dependent on the presence of either glucose or peptone and oxygen. Induction of optimal activity required the simultaneous presence of glucose and peptone. At least 30% of maximal activity was induced in 5 hr in the presence of 0.4 µM MnSO₄. Actinomycin D (5 µg/ml) or chloramphenicol (35 µg/ml), when added to the induction medium, inhibited approximately 90% of MnO₂-reductase synthesis and incorporation of uracil-2-¹⁴C or leucine-1-¹⁴C. Cell-free extracts having MnO₂-reductase activity were prepared by sonic disruption of cell suspensions of induced Bacillus 29. Such extracts used glucose metabolism as a source of electrons. They had an average specific activity of 1.15 nmoles of Mn^II produced per mg of protein per hr at 25 C. They had a temperature optimum of 18 C for reductase activity and retained 50% of their activity at 4 C, the approximate temperature of the natural habitat of the organism. Extracts were stable for several days at 4 C but rapidly lost over 50% of their activity on freezing and thawing. Over 90% of the activity of the extract could be destroyed by heating in a boiling-water bath for 5 min. At a concentration of 1 mM, HgCl₂ and atebrine dihydrochloride inhibited MnO₂-reductase activity by at least 50%, but sodium azide was ineffective. The MnO₂-reductase activity of induced cells and extracts from them was no greater in the absence of oxygen than in its presence, confirming an earlier observation that MnO₂ and O₂ do not compete as terminal electron acceptors in the respiratory activity of this organism.

² Present address: Division of Laboratories and Research, New York State Department of Health, Albany, N. Y. 12201.

¹ Part of a dissertation submitted by the senior author to the Department of Biology of Rensselaer Polytechnic Institute in partial fulfillment of the requirements for the Ph.D. degree.