nanoscale_detection_of_organic_signatures_in__carbonate__microbialites

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1、NanoscaledetectionoforganicsignaturesincarbonatemicrobialitesKarimBenzerara§,NicolasMenguy,Purificacio´nLo´pez-Garcı´a¶,Tae-HyunYoon
,Jo´zefKazmierczak,TolekTyliszczak,Franc¸oisGuyot,andGordonE.Brown,Jr.§§InstitutdeMine´ralogieetdePhysiquedesMilieuxCo

2、ndense´s,Unite´MixtedeRecherche7590,CentreNationaldelaRechercheScientifique,DepartmentdeMine´ralogie,InstitutdePhysiqueduGlobedeParis,UniversityofParis6and7,140RuedeLourmel,75015Paris,France;SurfaceandAqueousGeochemistryGroup,DepartmentofGeologicaland

3、EnvironmentalSciences,StanfordUniversity,Stanford,CA94305-2115;¶Unite´dEcologie,Syste´matiqueetEvolution,Unite´MixtedeRecherche8079,CentreNationaldelaRechercheScientifique,Universite´Paris-Sud,91405OrsayCedex,France;
DepartmentofChemistry,HanyangUnive

4、rsity,Music17Haengdang-dong,Seongdong-gu,Seoul,133-791,Korea;InstituteofPaleobiology,PolishAcademyofSciences,Twarda5155,00818Warsaw,Poland;AdvancedLightSource,LawrenceBerkeleyNationalLaboratory,Berkeley,CA94720;and§§StanfordSynchrotronRadiationLabor

5、atory,StanfordLinearAcceleratorCenter,MS69,2575SandHillRoad,MenloPark,CA94025CommunicatedbyW.G.Ernst,StanfordUniversity,Stanford,CA,April21,2006(receivedforreviewJanuary12,2006)Microbialitesaresedimentarydepositsassociatedwithmicrobialmatcommunitiesa

6、ndarethoughttobeevidenceofsomeoftheoldestlifeonEarth.Despiteextensivestudiesofsuchdeposits,littleisknownabouttheroleofmicroorganismsintheirformation.Inaddition,unambiguouscriteriaprovingtheirbiogenicityhaveyettobeestablished.Inthisstudy,wecharacteriz

7、emoderncalcareousmicrobialitesfromthealkalineLakeVan,Turkey,atthenanometerscalebycombiningx-rayandelectronmicroscopies.Wedescribeasimplewaytolocatemicroorganismsentombedincalciumcarbonateprecipitatesbyprobingaromaticcarbonfunc-tionalgroupsandpeptideb

8、onds.Near-edgex-rayabsorptionfinestructurespectraattheCandNK-edgesprovideuniquesignaturesformicrobes.Aragonitecrystals,whichrangeinsizefrom30to100nm,comprisethelargestpartofthemicrobialites.Thesecrystalsaresurroundedbya10-nm-thickamorphouscalciumcarbo