Variability in Arsenic Methylation Efficiency across Aerobic and_ Anaerobic Microorganisms

VariabilityinArsenicMethylationEfficiencyacrossAerobicandAnaerobicMicroorganismsKarenViacava,KarinLederballeMeibom,DavidOrtega,ShannonDyer,ArnaudGelb,LeiaFalquet,NigelP.Minton,AdrienMestrot,andRizlanBernier-Latmani*CiteThis:https://dx.doi.org/10.1021/acs.est.0c03908ReadOnlineACCESSMetrics&MoreArticleRecommendations*sıSupportingInformationABSTRACT:Microbially-mediatedmethylationofarsenic(As)playsanimportantroleintheAsbiogeochemicalcycle,particularlyinricepaddysoilswheremethylatedAs,generatedmicrobially,istranslocatedintoricegrains.Thepresenceofthearsenite(As(III))methyltransferasegene(arsM)insoilmicrobeshasbeenusedasanindicationoftheircapacityforAsmethylation.Here,weevaluatetheabilityofsevenmicroorganismsencodingactiveArsMenzymestomethylateAs.Amongstthose,onlytheaerobicspecieswereefficientmethylators.TheanaerobicmicroorganismspresentedhighresistancetoAsexposure,presumablythroughtheirefficientAs(III)efflux,butmethylatedAspoorly.Theonlyexceptionweremethanogens,forwhichefficientAsmethylationwasseeminglyanartifactofmembranedisruption.Deletionofaneffluxpumpgene(acr3)inoneoftheanaerobes,Clostridiumpasteurianum,renderedthestrainsensitivetoAsandcapableofmoreefficientlymethylatingAs.Ourresultsledtothefollowingconclusions:(i)encodingafunctionalArsMenzymedoesnotguaranteethatamicroorganismwillactivelydriveAsmethylationinthepresenceofthemetalloidand(ii)thereisaninverserelationshipbetweenefficientmicrobialAseffluxanditsmethylation,becausetheformerpreventstheintracellularaccumulationofAs.KEYWORDS:Arsenic