Bacterial Methanogenesis and Growth from CO ₂ with Elemental Iron as the Sole Source of Electrons

Abstract

Previous studies of anaerobic biocorrosion have suggested that microbial sulfur and phosphorus products as well as cathodic hydrogen consumption may accelerate anaerobic metal oxidation. Methanogenic bacteria, which normally use molecular hydrogen (H(2)) and carbon dioxide (CO(2)) to produce methane (CH(4)) and which are major inhabitants of most anaerobic ecosystems, use either pure elemental iron (Fe(0)) or iron in mild steel as a source of electrons in the reduction of CO(2) to CH(4). These bacteria use Fe(0) oxidation for energy generation and growth. The mechanism of Fe(0) oxidation is cathodic depolarization, in which electrons from Fe(0) and H(+) from water produce H(2), which is then released for use by the methanogens; thermodynamic calculations show that significant Fe(0) oxidation will not occur in the absence of H(2) consumption by the methanogens. The data suggest that methanogens can be significant contributors to the corrosion of iron-containing materials in anaerobic environments.

Corrosion of Iron by Sulfate-Reducing Bacteria: New Views of an Old Problem

“…The previously observed acceleration of cathodic reactions in SRB cultures (65,(69)(70)(71) could now be explained by reaction between sulfide and iron rather than by microbial consumption of cathodic H 2 . Since then, occasional attempts to resurrect the theory have been made (38,42,(72)(73)(74), but to date, no culture-based experiment has been able to demonstrate that bacterial consumption of cathodic hydrogen accelerates iron corrosion to any significant extent (39,47,67,75). It should be stressed at this point that the study of a direct corrosive effect of SRB requires the use of essentially organic matter-free cultivation media to avoid unnecessary complication or even misinterpretation of data resulting from the corrosive effects of H 2 S.…”

“…Here, corrosion results from microbial metabolic products such as organic acids (27,28), hydrogen sulfide (12,29,30), or other corrosive sulfur species (31)(32)(33)(34). In addition to these indirect effects, more-direct interactions between certain microorganisms and iron have been demonstrated (12,(35)(36)(37)(38)(39).…”

“…Most studies have focused on the corrosive effects of sulfatereducing bacteria (SRB), but other physiological groups such as thiosulfate-reducing bacteria (40), nitrate-reducing bacteria (41)(42)(43)(44), acetogenic bacteria (45), and methanogenic archaea (38,39,(46)(47)(48)(49) have also been implicated in iron corrosion. Still, the physiological group of environmental microorganisms with a suggested key role in the anaerobic corrosion of iron consists of the SRB (5,6,50,51), which are widespread in many natural as well as engineered aquatic environments.…”

Enhancements to Natural Attenuation: Selected Case Studies

“…Another possible source for methane observed at the Elizabeth City PRB is methanogenesis by bacteria from dissolved CO 2 using elemental iron as the electron source. The latter process was demonstrated by Daniels et al (1987) in experiments wherein CH 4 was produced in iron/water/CO 2 systems inoculated with methanogenic bacteria but was not observed in uninoculated and sterilized controls.…”

Attachment of the adhesive holdfast organelle to the cellular stalk of Caulobacter crescentus

“…Complex associations and structures develop in such microbial films, resulting in such phenomena as gradations of redox potential and interdependent metabolic processes, such as interspecies hydrogen transfer (4,6).…”