Dissimilatory metal reducing bacteria in biogeochemistry and corrosion

Dissimilatory metal reducing bacteria (DMRB) have been recognized for their role in metal transformations in pristine and contaminated environments. These organisms can directly and indirectly reduce numerous minerals, toxic heavy metals, and radionuclides and may also alter the stability of important ferric oxide/hydroxide passive films, thereby, influencing corrosion cells. Direct biological reduction/dissolution of ferric iron-containing passive films may represent a mechanism of microbiologically influenced corrosion (MIC) that is unique to DMRB. The factors that influence mineral dissolution may therefore be important in understanding and minimizing this form of MIC. A thermodynamic evaluation of hematite bioreduction suggests that hematite films may not be as stable as predicted based upon accepted thermodynamic data. Known biogeochemical and environmental reactions are examined herein for their potential role in promoting or possibly preventing corrosion.