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Evidence for the coexistence of direct and riboflavin‐mediated interspecies electron transfer in Geobacter co‐culture
Author(s) -
Huang Lingyan,
Liu Xing,
Ye Yin,
Chen Man,
Zhou Shungui
Publication year - 2020
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.14842
Subject(s) - geobacter , geobacter sulfurreducens , biology , flavin group , electron transfer , cytochrome , biochemistry , microbiology and biotechnology , bacteria , chemistry , photochemistry , genetics , enzyme , biofilm
Summary Geobacter species can secrete free redox‐active flavins, but the role of these flavins in the interspecies electron transfer (IET) of Geobacter direct interspecies electron transfer (DIET) co‐culture is unknown. Here, we report the presence of a new riboflavin‐mediated interspecies electron transfer (RMIET) process in a traditional Geobacter DIET co‐culture; in this process, riboflavin contributes to IET by acting as a free‐form electron shuttle between free Geobacter species and serving as a bound cofactor of some cytochromes in Geobacter co‐culture aggregates. Multiple lines of evidence indicate that RMIET facilitates the primary initiation of syntrophic growth between Geobacter species before establishing the DIET co‐culture and provides additional ways alongside the DIET to transfer electrons to achieve electric syntrophy between Geobacter species. Redox kinetic analysis of riboflavin on either Geobacter species demonstrated that the Gmet_2896 cytochrome acts as the key riboflavin reduction site, while riboflavin oxidation by Geobacter sulfurreducens is the rate‐limiting step in RMIET, and the RMIET makes only a minor contribution to IET in Geobacter DIET co‐culture. The discovery of a new RMIET process in Geobacter DIET co‐culture suggests the complexity of IET in syntrophic bacterial communities and provides suggestions for the careful examination of the IET of other syntrophic co‐cultures.

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