Humic substances can mediate electron transfer between microorganisms and Fe(III) minerals. Because it is unknown which microorganisms reduce humics in anoxic aquifers, we analyzed the diversity and physiological flexibility of Fe(III)-, humics-, and AQDS-reducers, which were present at up to 106 cells g−1. No significant differences in 16S rRNA gene based diversity were found between enrichment cultures reducing ferrihydrite, humics or AQDS. Even after repeated transfers many of the enrichments retained the ability to switch to other electron acceptors. This suggests that humics- and Fe(III)-reducing microorganisms in anoxic aquifers are rather versatile and able to reduce different extracellular electron acceptors.
Bibliographical noteFunding Information:
Financial support came from Arcadis Deutschland GmbH (office Freiberg, Saxony), the Landesanstalt fu€r Altlastenfreis-tellung (Magdeburg, Saxony-Anhalt), and the Mitteldeutsche Sanierungs-und Entsorgungsgesellschaft (Bitterfeld, Saxony-Anhalt). Also, this research was funded by the German Research Foundation (DFG), research unit FOR 580 “Electron Transfer Processes in Anoxic Aquifers.”
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- Fe(III) reduction
- electron shuttling
- humic acids