Reduction of ferric iron by acidophilic heterotrophic bacteria: evidence for constitutive and inducible enzyme systems in Acidiphilium spp.
OBJECTIVE
To compare the abilities of two obligately acidophilic heterotrophic bacteria, Acidiphilium acidophilum and Acidiphilium SJH, to reduce ferric iron to ferrous when grown under different culture conditions.


RESULTS
Bacteria were grown in batch culture, under different aeration status, and in the presence of either ferrous or ferric iron. The specific rates of ferric iron reduction by fermenter-grown Acidiphilium SJH were unaffected by dissolved oxygen (DO) concentrations, while iron reduction by A. acidophilum was highly dependent on DO concentrations in the growth media. The ionic form of iron present (ferrous or ferric) had a minimal effect on the abilities of harvested cells to reduce ferric iron. Whole cell protein profiles of Acidiphilium SJH were very similar, regardless of the DO status of the growth medium, while additional proteins were present in A. acidophilum grown microaerobically compared with aerobically-grown cells.


CONCLUSIONS
The dissimilatory reduction of ferric iron is constitutive in Acidiphilium SJH while it is inducible in A. acidophilum.


CONCLUSIONS
Ferric iron reduction by Acidiphilium spp. may occur in oxygen-containing as well as anoxic acidic environments. This will detract from the effectiveness of bioremediation systems where removal of iron from polluted waters is mediated via oxidation and precipitation of the metal.
Johnson
D B
DB
School of Biological Sciences, University of Wales, Bangor, UK. d.b.johnson@bangor.ac.uk
Bridge
T A M
TA
D016947:Acetobacteraceae / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism*; D000332:Aerobiosis; D003470:Culture Media; D004790:Enzyme Induction; D038181:FMN Reductase; D005290:Ferric Compounds / Q000378:metabolism*; D007700:Kinetics; D009247:NADH, NADPH Oxidoreductases / Q000096:biosynthesis / Q000378:metabolism*
D003470:Culture Media; D005290:Ferric Compounds; D038181:FMN Reductase; D009247:NADH, NADPH Oxidoreductases; C023903:ferric citrate iron reductase