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JeffreyGralnickUniversityofMinnesota
DepartmentofPlantandMicrobialBiologyDirector,MicrobialandPlantGenomeInstitute
[email protected] @bacteriality
Drivingmicrobialmetabolismwithelectricity:challengesandopportunitiesinelectrosynthesis
ISF-2DOEListeningDay
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Fe(II)
e- Fe(III)
e-
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e-Cathode
RenewableElectricity
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Outline
Fe(II)
e- Fe(III)
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• Oxygen• Nitrate• Nitrite• TMAO• DMSO• Sulfur• Fumarate• Urocanate
• Chromium• Selenium• Arsenic• Technetium• Uranium• Tellurium• Cobalt• Vanadium• Manganese• Iron
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• Oxygen• Nitrate• Nitrite• TMAO• DMSO• Sulfur• Fumarate• Urocanate
• Chromium• Selenium• Arsenic• Technetium• Uranium• Tellurium• Cobalt• Vanadium
• Manganese• Iron
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Iron Oxide Manganese Oxide
“Extracellular Electron Transport”
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Respiration of insoluble substrates
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MtrF – aparalog ofMtrC inS.oneidensis
MtrCMtrBMtrA
CymA
Clarkeetal.,2011PNASJun7;108(23):9384-9
Core conduit for EET in Shewanella
CctA/FccAMQH2 MQ
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Cur
rent
(μA)
Time (hours)0 10 20 30 40 50 60 70 80
0
10
20
30
40
MR-1
Time (h)
RespirationofcarbonelectrodesbyShewanella
Lactate Acetate+ATP+4e- +4H+
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Electrode-dependentfumaratereduction
OutwardElectronFlow ReverseElectronFlow
CathodeAnode
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Electrode-dependentfumaratereduction
0.0 0.2 0.4 0.6 0.8 1.0-15
-10
-5
0
50 mM fumarate
WT
Time (hours)
Curr
ent D
ensi
ty (µ
A/c
m2)
Ross et al., PLoS One, 2011
Cathode
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Electrode-dependentfumaratereductionrequiresFccA (thefumaratereducatase)
0.0 0.2 0.4 0.6 0.8 1.0-15
-10
-5
0
50 mM fumarate
WT
!fccA
Time (hours)
Curr
ent D
ensi
ty (µ
A/c
m2)
X
Cathode
Ross et al., PLoS One, 2011
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TheMtr respiratorypathwaycatalyzesreversibleelectrontransfer
0.0 0.5 1.0 1.5-15
-10
-5
0
50mM Fumarate
!mtrB
WT
Time (hours)
Curr
ent D
ensity (µ
A/c
m2)
XCathode
Ross et al., PLoS One, 2011
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TheMtr respiratorypathwaycatalyzesreversibleelectrontransfer
0.0 0.5 1.0 1.5-15
-10
-5
0
50mM Fumarate
WT
!mtrB
!mtrA
Time (hours)
Curr
ent D
ensity (µ
A/c
m2)
X
Cathode
Ross et al., PLoS One, 2011
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X
Cathode
Ross et al., PLoS One, 2011
0.0 0.5 1.0 1.5-15
-10
-5
0
!cymA
50mM Fumarate
!mtrB
WT
!mtrA
Time (hours)
Curr
ent D
ensity (µ
A/c
m2)
Thequinone oxidoreductaseCymA isrequiredforrobustinwardelectronflow
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Cathode
Ross et al., PLoS One, 2011
0.0 0.5 1.0 1.5-15
-10
-5
0
!cymA
50mM Fumarate
!mtrB
WT
!mtrA
Time (hours)
Curr
ent D
ensity (µ
A/c
m2)
X
Thequinone oxidoreductaseCymA isrequiredforrobustinwardelectronflow
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Menaquinone isimportantforrobustinwardelectronflow
Cathode
Ross et al., PLoS One, 2011
0.0 0.5 1.0 1.5-15
-10
-5
0
50mM Fumarate
WT
!mtrB
!mtrA
menC
!cymA
Time (hours)
Curr
ent D
ensity (µ
A/c
m2)
X
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Shewanella cannotfixCO2
RobustATPandNAD(P)HproductionwouldrequireO2 asanelectronacceptor.AnaerobicmetabolismandEETareHIGHLYrepressedbyO2.
IronrespirationisthoughttobeoneoftheearliestformsofrespirationonEarth– that’salotofselectionforsendingelectronsOUTofthesystemratherthanin.
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Fe(II)
e- Fe(III)
e-
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Fe2+ +0.25O2 +2.5H2O→Fe(OH)3 + 2H+
Mariprofundus ferrooxydans PV-1
Foundingmember:ZetaproteobacteriaObligateFe(II)oxidizerNeutrophillicChemolithoautotrophRuBisCo usedtofixCO2 Fe(II)
Fe(III)
e-
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Mariprofundus ferrooxydans PV-1
Chan
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Fe2+ +0.25O2 +2.5H2O→Fe(OH)3 + 2H+
Mariprofundus ferrooxydans PV-1
Chan
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Fe(III) oxides
Chan
Ifthemechanismofobtaininge-fromFe(II)isextracellular,weshouldbeabletoreplaceFe(II)withacathode.
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GrowthofMariprofundus usingacathode
Summers et al., mBio, 2013
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GrowthofMariprofundus usingacathode
Summers et al., mBio, 2013
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MicrobialBiocatalysis• Self-sufficient• Self-replicating• Self-contained• Self-optimizing• Canbemanipulatedusing
syntheticbiologyandgenetics
Bioelectrochemical Catalysis
Bioelectrochemicalcatalysis
Substrate
Product
2e-
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Acknowledgements
• ClaraChan,UniversityofDelaware
• DanielBond,UniversityofMinnesota
@bacteriality