Reduction of ferric iron by acidophilic heterotrophic bacteria: evidence for constitutive and inducible enzyme systems in Acidiphilium spp.

AIMS: 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. METHODS AND 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. SIGNIFICANCE AND IMPACT OF THE STUDY: 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.

Extracellular metal-binding activity of the sulphate-reducing bacterium Desulfococcus multivorans.

Polarography was used to measure the copper-binding ability of culture filtrates from a range of sulphate-reducing bacteria (SRB), including pure cultures and environmental isolates. Of those tested, Desulfococcus multivorans was shown to have the greatest copper-binding capacity and this organism was used for further experiments. Extracellular copper- and zinc-binding activities of Dc. multivorans culture filtrates from batch cultures increased over time and reached a maximum after 10 d growth. The culture filtrate was shown to bind copper reversibly and zinc irreversibly. Twelve-day-old Dc. multivorans culture filtrates were shown to have a copper-binding capacity of 3.64 +/- 0.33 micromol ml(-1) with a stability constant, log10K, of 5.68 +/- 0.64 (n=4). The metal-binding compound was partially purified from culture growth media by dichloromethane extraction followed by HPLC using an acetonitrile gradient.

Pediatric carbamazepine overdoses.

Thirty pediatric cases of carbamazepine overdoses were reviewed retrospectively for the frequency of toxic effects. Patients were divided into three groups, depending on the type of overdose: acute, acute-on-chronic, and chronic. Effects included lethargy in 93%, ataxia in 50%, nystagmus in 13%, and minor arrhythmias in 10%. Major effects included seizures in 20%, coma in 27%, and need for intubation in 20%. Higher serum carbamazepine levels were associated with these major effects in the acute and acute-on-chronic groups but not in the chronic group. Serum levels greater than 35 mg/L (147 mumol/L), were significantly associated with major toxicities.