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PubMed2000

Bacterial reduction of copper-contaminated ferric oxide: copper toxicity and the interaction between fermentative and iron-reducing bacteria.

Fe(III) oxide is an important heavy-metal sink, and bacteria are responsible for much of the Fe(III) reduced in nonsulfidogenic aquatic environments, yet factors governing the bacterial reduction of heavy metal-contaminated iron oxide are largely unknown. In this study with a stabilized bacterial consortium enriched from metal-contaminated sediments, we demonstrate that Cu toxicity impedes anaerobic carbon oxidation and bacterial reduction of hydrous ferric oxide (HFO). In the enrichment culture, a Clostridium sp. fermented lactate to propionate and acetate and Fe(III) reducers coupled acetate oxidation to HFO reduction. Increasing the amount of Cu in the culture medium significantly extended the time before Fe(III) reduction occurred and decreased the reduction rate, but did not affect the extent of HFO reduction. The Clostridium had a higher Cu-complexation capacity than the Fe(III) reducer Shewanella alga. Iron reduction was inhibited until almost all of the dissolved Cu was removed from solution and occurred two to seven times faster if the sediment enrichment culture was fed lactate instead of acetate. Our findings suggest that fermentative bacteria play a role in ameliorating heavy metal toxicity to iron-reducing bacteria. Fermenters may therefore enhance metal release in sediments by facilitating the bacterial reductive dissolution of heavy metal-contaminated HFO.

Bacteria↗
PubMed1975

Studies on the reconstitution of bovine erythrocyte superoxide dismutase. V. Preparation and properties of derivatives in which both zinc and copper sites contain copper.

1. We have developed a procedure for preparing derivatives of bovine superoxide dismutase in which primarily the Cu binding sites are occupied by Cu2+ (2 Cu2+-) and in which both the Zn and Cu binding sites are occupied by Cu2+ (4 Cu2+-). 2. The 2 Cu2+ protein shows approximately one-half the superoxide dismutase activity of an equivalent amount of native protein. A two-fold enhancement of the activity of 2 Cu2+-dismutase was observed upon occupation of the Zn sites either with Zn2+ or Cu2+. 3. The electron paramagnetic resonance spectrum of 4 Cu2+ protein was recorded over the temperature range 5-100 degrees K and the results suggest an antiferro-magnetic interaction between Cu2+ in the Zn site and Cu2+ in the Cu site having a coupling constant of approx. 52 cm-1. 4. The binuclear Cu2+ complex was found to accept only one electron from ferrocyanide. 5. One-half the total Cu+ of dithionite reduced 4 Cu+ protein was found to react rapidly with bathocupreine sulfonate whereas the other half reacted slowly. Reduced native protein did not react with bathocupreine sulfonate below 70 degrees C.

Animals↗