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Extracts prepared from a halophilic bacterium contained a reduced nicotinamide adenine dinucleotide (NADH2) oxidase active at high solute concentrations. The cation requirement was nonspecific, since KCI, RbCl, and CsCl replaced NaCl with little or no loss of activity, and NH4C1 was only partially effective. Only LiCI failed to replace NaCl. No specific chloride requirement was observed although not all anions replaced chloride. Bromide, nitrate, and iodide were essentially ineffective, whereas acetate, formate, citrate, and sulfate proved suitable. The presence of sulfate affected the ability of a cation to satisfy the solute requirement. Sulfate enhanced the rate of NADH2 oxidation when compared with the rate observed in the presence of chloride. Cations which were inactive as chlorides (LiCl and MgC12 at high concentrations) satisfied the cation requirement when added as sulfate salts. Although magnesium satisfied the cation requirement, a concentration effect, as well as an anion effect, was observed. In the presence of MgCl2, little NADH2 oxidation was observed at concentrations greater than 1 M. At lower concentrations, the rate of oxidation increased, reaching a maximal value at 0.1 M and remaining constant up to a concentration of 0.05 M MgCl2. Magnesium acetate and MgSO4 also replaced NaCl, and the maximal rate of oxidation occurred at 0.05 M with respect to magnesium. There was no change in the rate of oxidation at high magnesium acetate concentrations, whereas the rate of NADH2 oxidation increased at higher concentrations of MgSO4.

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Cell-free extracts prepared from the extremely halophilic bacterium Halobacterium saccharovorum oxidize galactose and accumulate a product which reacts as if it were a lactone. The product does not act as a reducing sugar and contains all six of the carbon atoms initially present in galactose. The product was jugged to be galactonic acid, based on the behavior of the acetylmethyl ester derivative of the product and the pentaacetyl derivative of the galactonic methyl ester during gas chromatography.

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