Jay V. Beck

Chalcocite Oxidation and Coupled Carbon Dioxide Fixation by Thiobacillus ferrooxidans

The reaction of cell suspensions of Thiobacillus ferrooxidans with pulverized chalcocite (Cu2S) in a Warburg manometric apparatus resulted in oxygen uptake accompanied by increased solubilization of copper and fixation of carbon dioxide. Since the only detectable oxidized products were cupric ions and the more oxidized form of the sulfide mineral, that is, digenite or covellite, the apparent source of energy for the carbon dioxide fixation was provided by the oxidation of the cuprous copper of the chalcocite.

Studies on a ferrous-ion-oxidizing bacterium. II. Cytochrome composition☆

Abstract 1. 1. Cells of an iron-oxidizing bacterium have been shown to contain both cytochrome c and cytochrome a 1 . No cytochrome b was detected in whole cells or cell-free extracts. 2. 2. The cytochrome c was partially purified and had absorption maxima at 552, 523, and 417 mμ. Pyridine and cyanide hemochromogens showed it to be a c type cytochrome. The E 0 ′ at pH 7.0 was 0.31 v., while at pH 2.9 the potential was 0.38 v. The cytochrome was not oxidized by the air, and its concentration in the cell was 88 mg./g. nitrogen. 3. 3. Both the cytochrome c and cytochrome a 1 were reduced when ferrous ion was added to a cell suspension. The relation of the cytochrome composition to the physiology of the organism is discussed, and it is proposed that the biological oxidation of iron involves a transfer of electrons from iron to cytochrome c, cytochrome a 1 , and oxygen in that sequence.

Competitive inhibition of phosphoribulokinase by AMP

Abstract The inhibition of ATP-dependent CO2 fixation by AMP has been observed in cell-free extracts of Thiobacillus , thioparus , T. , novellus , Chromatium , D , spinach, and T. , ferrooxidans (Johnson and Peck, 1965 ; Mayeux and Johnson, 1966 ; Johnson, 1966 ; and Gale 1966). The locus of the inhibition is apparently phosphoribulokinase and it has been suggested (Johnson, 1966) that the mechanism involves some direct action by AMP on the enzyme, which is not competitive inhibition. The present studies conducted on cell-free extracts of T. , ferrooxidans indicate that the inhibition of CO2 fixation by AMP is of a competitive nature between AMP and the normal substrate ATP for the phosphoribulokinase enzyme.