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Sulfurcycle

•  Overviewofsulfurcycle•  Sulfuroxida7onpathways•  Sulfurreduc7onpathways•  SurveyingS‐metabolizingac7vity

TheSulfurCycle

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SulfurAssimila7onReduc7onofsulfatetosulfideoccursinaseriesofstepsandinvolvesthesulfur‐containingproteinthioredoxin.

Somemicroorganismscanassimilateotherformsofsulfur,suchassulfuresters(R‐CH2OSO3

–),sulfonates(R‐CH2SO3–),sulfur‐

containingaminoacids,orothercarbon–sulfurcompounds.

Figure 10.25 Sulfur assimilation (Part 1)

Figure 10.25 Sulfur assimilation (Part 2) Figure 10.25 Sulfur assimilation (Part 3)

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Assimila7onvs.Dissimila7on

Electronscomefromtheelectrontransportchain

dSiRDissimilatory

SulfiteReductaseDsrAB

aSiR

Oxida7onofSulfurcompounds S2‐/S

S2‐/SO42‐

Beggiatoa(S2−−>S0)(O2aselectronacceptor)

Tubeworm:Ry*iapachyp/laSymbion7cbacteria(S2−−>S0withO2)(S2‐fromhydrothemalvents)

Ecologyofsulfide‐oxidizingmicroorganismsSulfuroxidizingarchaeonSulfolobus acidocaldarius

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AcidiphilicSulfuroxidizingThiobacillus

1.  ThiobacillusthiooxidansThiobacillusferrooxidans

2.  Producessulfuricacid(H2SO4)–  Acidifica7onofsoil

–  Dissolu7onofminerals,e.g.CaCO3

Reactions ∆G˚’ kJ/mol

H2S + 2 O2 >>> SO42- + 2H+ -798.2

HS- + 1/2O2 + H+ >>> S0 + H2O -209

S0 + H2O + 1.5 O2 >>> SO42- + 2H+ -587

S2O32- + H2O + 2O2 >>> 2 SO4

2- + 2H+ -818

SulfurOxidizingBetaproteobacteria•  Someusesulfideastheenergysource(intheformofH2S),ormetalsulfides.

•  Someuseelementalsulfur(S0),andotherusethiosulfate,(S2O3

2–).•  Thefinalproductinallcasesissulfuricacid,whichlowersthepHduringgrowth.

Theoverallreac7onsareasfollowed:

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Soxida7oninacidiphilicproteobacteria

SQR:Sulfide:quinonereductase

SAR:Sulfite:acceptoroxidoreductase

TQO:Thiosulfate:quinoneoxidoreductase

TTH:Tetrathionatehydrolase

O2

SDO:Sulfurdioxygenase

RohwerderandSand.Oxida7onofinorganicsulfurcompoundsinacidophilicprokaryotes.Eng.LifeSci.(2007)vol.7(4)pp.301‐309

Oxida7onofsulfurcompoundsbyThiobacillus(Part1)

ReverseoftheSulfateassimila7onpathway.

Figure19.23Oxida7onofsulfurcompoundsbyThiobacillus(Part2) Figure19.24Thiobacillus

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AcidophilicArchaea:Solfolobales

SQR:Sulfide:quinonereductase

SAR:Sulfite:acceptoroxidoreductase

TQO:Thiosulfate:quinoneoxidoreductase

TTH:Tetrathionatehydrolase

SOR:Sulfuroxygenasereductase

O2

RohwerderandSand.Oxida7onofinorganicsulfurcompoundsinacidophilicprokaryotes.Eng.LifeSci.(2007)vol.7(4)pp.301‐309

Sulfuroxida7oninanarchaeon

Kletzinetal..JBioenergBiomembr(2004)vol.36(1)pp.77‐91

Soxida7onisinnon‐acidiphiles

•  SulfuroxidizersuseenzymesintheSox•  GensinthesoxXYZABCD•  Theenzymesareperiplasmicinloca7on

•  Proteinscontainvariousmetalcofactors

•  CaninteractwithavarietyofinorganicScompoundsandcoupleoxida7ontoaerobicrespira7on

Friedrichetal.Prokaryo7csulfuroxida7on.CurrOpinMicrobiol(2005)vol.8(3)pp.253‐259

soxgenesinotherneutrophilicSoxidizers

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Figure1Modelofthereac7oncycleofthiosulfateoxida7onbytheSoxenzymesystemofP.pantotrophus(2,altered,withpermission.Copyright2001AmericanSocietyforMicrobiology).XA,heterodimericcytochromeccomplexSoxXA;B,dimanganesesulfate‐thioesteraseSoxB;YZ,sulfur‐bindingcomplexSoxYZ;CD,α2β2‐heterotetramericSoxCDcomplexofthemolybdoproteinSoxCandthecytochromecSoxD.

Publishedin:ArminQuentmeier;PetraJanning;PetraHellwig;CorneliusG.Friedrich;Biochemistry2007,46,10990‐10998.DOI:10.1021/bi700378kCopyright©2007AmericanChemicalSociety

SoxYZchaperonforScompounds

SoxXAThiosulfateOxidase

SoxCDSulfurDehydrogenase

SoxBDimanganesesulfate‐thioesterase

SoxXYZABCDSmetabolisminphototrophs

Sakuraietal.Inorganicsulfuroxidizingsystemingreensulfurbacteria.PhotosynthesisResearch(2010)vol.104(2‐3)pp.163‐76

Sulfide/sulfateredoxpoten7al

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Sulfatereducingbacteria•  Deltaproteobacteria•  Desulfovibriospeices

•  Strictanaerobes

•  Generateenergybyrespira7onofsulfurcompounds

•  SomecanuseH2forenergy

•  Manyuselactate,acetate,and/orethanolascarbonandenergysources.

•  Abundantinanaerobicaqua7cenvironmentswheresulfateishigh

–  Seawater

•  Alsoabundantinanaerobicenvironmentswithlotsofdecomposingorganicmaker

www.genomenewsnetwork.org

picasaweb.google.com/sd.gibson

Sulfaterespira7on

•  Sulfate,mostoxidizedformofsulfur•  Majoranionofseawater•  Sulfatereduc7ontohydrogensulfideoccursinanaerobicenvironments

•  Organotrophicorautotrophic–  Organicacidsandalcoholselectrondonors/e‐sources–  H2e‐donor,CO2carbonsource.

•  Sulfaterequiresac7va7onbeforeitcanbereduced.•  Assimila7veanddissimila7vereduc7onhavedifferentbiochemicalpathways.

MuyzerandStams.Theecologyandbiotechnologyofsulphate‐reducingbacteria.NatRevMicrobiol(2008)vol.6(6)pp.441‐54

MuyzerandStams.Theecologyandbiotechnologyofsulphate‐reducingbacteria.NatRevMicrobiol(2008)vol.6(6)pp.441‐54

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MuyzerandStams.Theecologyandbiotechnologyofsulphate‐reducingbacteria.NatRevMicrobiol(2008)vol.6(6)pp.441‐54

Dissimilatorysulfatereduc7on

•  Usestheassimilatorysulfatereductasetoac7vatesulfate– APS(adenosine‐phosphosulfate)

•  ApscomplexcovertsAPSintosulfite

•  ThenDSRreducessulfitetoHS•  Presentinmostsulfatereducers

•  Usedasafunc7onalgenemarkerinmicrobialecologystudies.

ElectronTransportChainOfSulfatereducingbacteria

pHgradient Enzymes:1.  ATPsulfurylase2.  APSreductase3.  Sulfitereductase

Carbonsource:Lactateoxida7oncangenerateH2andATPviasubstratelevelphosphoryla7on

Thesulfatereduc7onpathwayinDesulfovibriovulgaris

Oliveiraetal.ThecrystalstructureofDesulfovibriovulgarisdissimilatorysulfitereductaseboundtoDsrCprovidesnovelinsightsintothemechanismofsulfaterespira7on.JBiolChem(2008)vol.283(49)pp.34141‐9

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NewspinondsrA:reversedsrAinphototrophs Detec7onofSRB’s

•  Culturedependentmethods– MPN–  35Sulfateincorpora7on–  35Sradioisotopetracerstudies

•  Moleculardetec7onof:– apsABgene– dsrABgenes

•  Quan7ta7vedetec7on:– Real7mePCR