Reduction of Ferric Iron by Heterotrophic Bacteria in Lake Sediments

Abstract

The addition of Fe(II1) to anoxic lake sediments decreased the quantity of volatile fatty acids which accumulated. Similarly, the addition of several substrates to the sediments stimulated the rate of reduction of the naturally occurring Fe(II1). Of the substrates used, malate caused the greatest stimulation, and subsequently a malate-fermenting Vibrio was isolated from the sediment. This organism also reduced NO, and Mn(IV), the addition of which to the growth medium significantly lowered the rate of Fe(1I) formation. The presence of Fe(II1) in the medium increased the molar growth yield by 28% and this did not appear to be associated with the presence of particulate matter or changes in pH and E,,. The addition of Fe(II1) to the growth medium also produced a minor shift in the fermentation end-products, with a decrease in the quantity of ethanol formed and a concomitant increase in volatile fatty acids, both of which were of the same order as the amount of Fe(II1) reduced. It would appear, therefore, that the presence of Fe(II1) might permit a slight diversion of metabolism to more energetically favourable end products. The scale of iron reduction, both in the field and the laboratory, was very small compared with the reducing potential of the available substrates. ~ ~~~Abbreiiation: VFA, volatile fatty acid.0022-I 287/84/000 1 -1 282 $02.00 0 1984 SG M

Denitrovibrio acetiphilus, a novel genus and species of dissimilatory nitrate-reducing bacterium isolated from an oil reservoir model column.

“…nov. NRB also perform iron reduction (Sørensen, 1982 ;Jones et al, 1983Jones et al, , 1984Lovley & Phillips, 1988), we wanted to test strain N2460 T for this trait. As mentioned, however, ferric pyrophosphate reacted chemically with sulfide in the medium, raising the redox potential and causing growth inhibition of the bacterium.…”

Dissimilatory Fe(III) and Mn(IV) Reduction

“…transferred only 0.13 or 0.03% of the reducing equivalents available in glucose or malate to Fe(III) (159). Malate fermentation resulted primarily in the accumulation of organic acids and ethanol.…”

“…Starkey and Halverson (289) found that Fe(III) was reduced in anaerobic cultures of Clostridium sporogenes or E. coli growing in a glucose or peptone medium, and Roberts (272) found that Bacillus polymyxa reduced Fe(III) while fermenting glucose. Subsequent studies found that a wide variety of fermentative microorganisms reduced Fe(III) or Mn(IV) during anaerobic growth (45,46,128,158,159,226,245,246), and organisms capable of reducing Fe(III) and Mn(IV) under aerobic culture conditions have also been described (76,82,86,316).…”

“…The restriction of Fe(III) and Mn(IV) reduction to narrow zones near the sediment-water interface in many aquatic sediments makes determination of the in situ rates of Fe(III) and Mn(IV) reduction difficult. Rates of Fe(III) and Mn(IV) reduction in sediments have typically been estimated from the accumulation of Fe(II) and Mn(II) in anaerobic laboratory incubations of sediments (91,159,164,193,197,211,275,286). However, such measurements do not account for the fact that the supply of electron acceptors for potentially competing processes such as oxygen and nitrate reduction have been eliminated (193).…”

Distribution of iron-solubilizing bacteria in the sediment of a small lagoon.

“…Ottow3) re ported that iron reducers belownged to family Enterobacteriaceae, Bacillaceae, methanogenic clostridia, or sulfate reducing bacteria. Jones et al 5,6) found a strain of Vibrio has high activity in producting acetic acid and in reducing iron. In this study, the dominant genera of iron-sol ubilizing bacteria were Bacillus, Lactobacillus, and …”