Dissimilatory metal-reducing bacteria

Dissimilatory metal-reducing bacteria (DMRB) are a class of bacteria that couple the oxidation of organic matter to the reduction of a metal species in the process of anaerobic respiration. Species that typically use ferric iron as an electron acceptor are also known as dissimilatory iron-reducing bacteria (DIRB). In addition to Bacteria, some Archaea also perform dissimilatory iron (III) reduction, which suggests that microbial iron respiration may be one of the oldest forms of metabolism on earth.

DMRB include both obligate (strict) anaerobes, such as the Geobacteraceae family, and facultative anaerobes, such as Shewanella spp. Some species of DMRB produce compounds that act as electron shuttles, enabling them to perform metal reduction from a distance. Other organic compounds frequently found in soils and sediments, such as humic acids, may also act as electron shuttles.

A wide range of Fe(III)-bearing minerals have been observed to function as terminal electron acceptors, including magnetite, hematite, goethite, lepidocrocite, ferrihydrite, hydrous ferric oxide, smectite, illite, jarosite, among others.

In natural systems, secondary minerals may form as a byproduct of bacterial metal reduction. Commonly observed secondary minerals produced during experimental bio-reduction by DMRB include magnetite, siderite, green rust, vivianite, and hydrous Fe(II)-carbonate.

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