Effect of nitrate on reduction of ferric iron by a bacterium isolated from crude oil

Abstract

A Pseudomonas sp. isolated from crude oil reduced ferric ions (Fe(III)) to ferrous ions (Fe(II)). In the presence of nitrate (NO3-) after prolonged incubation, the amount of Fe(II) was lower than in its absence. However, during short incubation periods, the presence of NO3- significantly increased (99.5% confidence limit) the amount of Fe(II) produced. The decrease in Fe(II) on prolonged incubation was associated with increased production and accumulation of nitrite (NO2-). Under low NO3- levels, where the production of NO2- was limited, a decrease in NO2- concentration was accompanied by an increase in Fe(II) production to levels comparable with those obtained in the absence of NO3-. Preinduction of cells for nitrate reductase, which favoured rapid NO2- production, resulted in a more rapid decrease in Fe(II) production than in cells that were not preinduced. It is proposed that the inhibitory effect of NO3- on microbial reduction of Fe(III) is due to a secondary reaction, which involves the chemical oxidation of Fe(II) by NO2-.

Anaerobic Respiration Using Fe 3+ , S 0 , and H 2 in the Chemolithoautotrophic Bacterium Acidithiobacillus ferrooxidans

“…This suggests that the this c-type cytochrome is functional for anaerobic respiration involving Fe 3ϩ as an electron acceptor. There is growing evidence that cytochromes are involved in anaerobic metal reduction, serving as components in the respiratory chains of numerous bacteria (1,6,13,23,(27)(28)(29)31). Indeed, the c-type cytochrome described here would play an important part in anaerobic respiration as one of the electron transfer proteins in A. ferrooxidans.…”

Dissimilatory Fe(III) and Mn(IV) Reduction

“…Fe(III)-and Mn(IV)-reducing microorganisms have been enumerated and cultured on a wide variety of solid, semisolid, and liquid media that are similar in composition to those used for other heterotrophic microorganisms but with the modification that some form of Fe(III) or Mn(IV) was included in the medium. Naturally occurring Fe(III) or Mn(IV) oxides have been employed, as have hematite, goethite, lepidocrocite, synthetic poorly crystalline Fe(III) oxides, FePO4, FeCl3, and Fe(III) citrate (17,45,91,116,155,172,198,236,246,256,282,285,318). For agar media, the Fe(III) or Mn(IV) may be added as an overlay (89,230).…”

“…HQNO and carbon monoxide inhibited Fe(III) reduction in anaerobic suspensions of aerobically grown S. putrefaciens (235,236 (198). Direct contact between Fe(III) oxide and GS-15 were required for Fe(III) reduction (198).…”

“…The Fe(III) reductase activity in GS-15 was localized in the membrane fraction (117 (223,226,241,242,246,248). However, this inhibition can also be attributed to preferential electron flow to nitrate reductase rather than Fe(III) reductase (179) or to chemical oxidation of Fe(II) by nitrite produced during nitrate reduction (179,236). The other claim for involvement of nitrate reductase was that in a medium without nitrate, mutants that could no longer reduce nitrate produced less Fe(II) than did their wild-type counterparts (244).…”

Effects of nitrate and nitrite on dissimilatory iron reduction by Shewanella putrefaciens 200

“…Thus, the lack of Fe3+ reduction activity was apparently due to competitive inhibition by NO3-. Subsequently, several investigators hypothesized that NO3-inhibition of Fe3+ reductase activity was primarily the result of secondary (i.e., postreduction) chemical reoxidation of bacterially produced ferrous iron (Fe2+) by nitrite (N02-) (6,11).…”