JeffreyGralnickUniversityofMinnesota

DepartmentofPlantandMicrobialBiologyDirector,MicrobialandPlantGenomeInstitute

gralnick@umn.edu@bacteriality

Drivingmicrobialmetabolismwithelectricity:challengesandopportunitiesinelectrosynthesis

ISF-2DOEListeningDay

Outline

Fe(II)

e- Fe(III)

e-

Fe(II)

e-

e-

e-

e-CathodeAnode

e-Cathode

RenewableElectricity

Outline

Fe(II)

e- Fe(III)

• Oxygen• Nitrate• Nitrite• TMAO• DMSO• Sulfur• Fumarate• Urocanate

• Chromium• Selenium• Arsenic• Technetium• Uranium• Tellurium• Cobalt• Vanadium• Manganese• Iron

• Oxygen• Nitrate• Nitrite• TMAO• DMSO• Sulfur• Fumarate• Urocanate

• Chromium• Selenium• Arsenic• Technetium• Uranium• Tellurium• Cobalt• Vanadium

• Manganese• Iron

Iron Oxide Manganese Oxide

“Extracellular Electron Transport”

Respiration of insoluble substrates

MtrF – aparalog ofMtrC inS.oneidensis

MtrCMtrBMtrA

CymA

Clarkeetal.,2011PNASJun7;108(23):9384-9

Core conduit for EET in Shewanella

CctA/FccAMQH2 MQ

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+

Electrode-dependentfumaratereduction

OutwardElectronFlow ReverseElectronFlow

CathodeAnode

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

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

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

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

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

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

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

Shewanella cannotfixCO2

RobustATPandNAD(P)HproductionwouldrequireO2 asanelectronacceptor.AnaerobicmetabolismandEETareHIGHLYrepressedbyO2.

IronrespirationisthoughttobeoneoftheearliestformsofrespirationonEarth– that’salotofselectionforsendingelectronsOUTofthesystemratherthanin.

Fe(II)

e- Fe(III)

e-

Fe2+ +0.25O2 +2.5H2O→Fe(OH)3 + 2H+

Mariprofundus ferrooxydans PV-1

Foundingmember:ZetaproteobacteriaObligateFe(II)oxidizerNeutrophillicChemolithoautotrophRuBisCo usedtofixCO2 Fe(II)

Fe(III)

e-

Mariprofundus ferrooxydans PV-1

Chan

Fe2+ +0.25O2 +2.5H2O→Fe(OH)3 + 2H+

Mariprofundus ferrooxydans PV-1

Chan

Fe(III) oxides

Chan

Ifthemechanismofobtaininge-fromFe(II)isextracellular,weshouldbeabletoreplaceFe(II)withacathode.

GrowthofMariprofundus usingacathode

Summers et al., mBio, 2013

GrowthofMariprofundus usingacathode

Summers et al., mBio, 2013

MicrobialBiocatalysis• Self-sufficient• Self-replicating• Self-contained• Self-optimizing• Canbemanipulatedusing

syntheticbiologyandgenetics

Bioelectrochemical Catalysis

Bioelectrochemicalcatalysis

Substrate

Product

2e-

Acknowledgements

• ClaraChan,UniversityofDelaware

• DanielBond,UniversityofMinnesota

@bacteriality