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Geobacter sulfurreducens inner membrane cytochrome CbcBA controls electron transfer and growth yield near the energetic limit of respiration
Author(s) -
Joshi Komal,
Chan Chi Ho,
Bond Daniel R.
Publication year - 2021
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.14801
Subject(s) - geobacter sulfurreducens , electron transfer , redox , cytochrome , biology , electron acceptor , electron transport chain , geobacter , cytochrome c , anaerobic respiration , biophysics , yield (engineering) , biochemistry , bacteria , chemistry , inorganic chemistry , photochemistry , materials science , biofilm , mitochondrion , enzyme , metallurgy , genetics
Geobacter sulfurreducens utilizes extracellular electron acceptors such as Mn(IV), Fe(III), syntrophic partners, and electrodes that vary from +0.4 to −0.3 V versus standard hydrogen electrode (SHE), representing a potential energy span that should require a highly branched electron transfer chain. Here we describe CbcBA, a bc ‐type cytochrome essential near the thermodynamic limit of respiration when acetate is the electron donor. Mutants‐lacking cbcBA ceased Fe(III) reduction at −0.21 V versus SHE, could not transfer electrons to electrodes between −0.21 and −0.28 V, and could not reduce the final 10%–35% of Fe(III) minerals. As redox potential decreased during Fe(III) reduction, cbcBA was induced with the aid of the regulator BccR to become one of the most highly expressed genes in G. sulfurreducens . Growth yield (CFU/mM Fe(II)) was 112% of WT in ∆ cbcBA , and deletion of cbcL (an unrelated bc ‐cytochrome essential near −0.15 V) in Δ cbcBA increased yield to 220%. Together with ImcH, which is required at high redox potentials, CbcBA represents a third cytoplasmic membrane oxidoreductase in G. sulfurreducens . This expanding list shows how metal‐reducing bacteria may constantly sense redox potential to adjust growth efficiency in changing environments.