Flavin-mediated extracellular electron transfer in Gram-positive bacteria Bacillus cereus DIF1 and Rhodococcus ruber DIF2

Abstract

A flavin-mediated EET process was reported here in two new isolated electrochemically active Gram-positive bacterial strains DIF1 and DIF2.

Type IV Pili-Independent Photocurrent Production by the Cyanobacterium Synechocystis sp. PCC 6803

“…Microbial cell-to-electrode electron transfer by Synechocystis must therefore be facilitated by an alternative, i.e., non-pili-mediated, mechanism, either by direct transfer from some other cell surface electron transport proteins or by mediated-transfer via unknown redox-shuttles excreted into the extracellular environment/electrolyte ( Saper et al, 2018 ; Wenzel et al, 2018 ). Secreted flavins have been detected in cultures of Shewanella and other bacteria and are believed to play a role in EET by serving as soluble redox mediators ( Okamoto et al, 2013 ; Tian et al, 2019 ).…”

Coproduction and enhancement of electricity and biobutanol using adsorption carrier solid-state fermentation

“…On the one hand, riboflavin can act as an electron shuttle to directly mediate electron transfer. On the other hand, riboflavin can act as a cofactor to improve the EET rate of other electron shuttles [ 26 ]. Therefore, Riboflavin concentration was detected.…”

Electroactivity across the cell wall of Gram-positive bacteria

“…These redox compounds can be a metabolite produced by the microorganism (e.g. flavins, phenazines, quinones) [62] , [63] , [64] or an artificial electron shuttle that can be added to the system (e.g. poly(MPC-co-VF), macrocyclic cobalt hexamines, osmium redox polymers) [57] , [65] , [66] .…”

“…PTH1 to achieve EET [39] . But later on, it was demonstrated that Gram-positive bacteria can also produce redox mediators, such as humic acids, quinones and flavins [16] , [44] , [61] , [62] , [67] . For example, Lactococcus lactis cells can catalyse EET to an electrode by the excretion of soluble quinones as redox mediators [45] , while spore-forming bacteria belonging to Bacillus genus have the ability to excrete flavins [41] , [61] , [62] , [68] , [69] , [70] .…”

“…to mediate electron transfer to electrodes in MFC [62] , [68] , and provide a boost to electricity generation in microbial consortia with Gram-negative bacteria or yeasts [60] , [69] , [70] . Recently, it was also shown that flavins are secreted by Rhodococcus ruber DIF2, and that flavin mononucleotide (FMN) plays an important role in the EET of this bacterium to electrodes [62] . Though humic acids were shown to support the generation of electricity of Desulfitobacterium hafniense strain DCB2, the specific electron shuttle responsible to mediate electron transfer to the electrode was not identified [44] .…”