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Regulationofarseniteoxidationbythephosphatetwo-componentsystemPhoBRinHalomonassp.HAL1

Fang Chen,YajingCao,ShaWei,YanzhiLi,XiangyangLi,QianWang* and GejiaoWang

Previously,theexpressionofarsenite[As(III)]oxidasegenesaioBAwasreportedtoberegulatedbyathree-componentregulatorysystem,AioXSR,inanumberofAs(III)-oxidizingbacterialstrains.However,theregulationmechanismisstillunknownwhenaioXSRgenesareabsentinsomeAs(III)-oxidizingbacterialgenomes,suchasinHalomonassp.HAL1.Inthisstudy,transposonmutagenesisandgeneknock-outmutationwereperformed,andtwomutants,HAL1-phoR931andHAL1-△phoB,wereobtainedinstrainHAL1.ThephoRandphoBconstituteatwo-componentsystemwhichisresponsibleforphosphate(Pi)acquisitionandassimilation.BothofthemutantsshowednegativeAs(III)-oxidationphenotypesinlowPicondition(0.1mM)butnotundernormalPicondition(1mM).ThephoBRcomplementationstrainHAL1-△phoB-Creversedthemutants’nullphenotypesbacktowildtypestatus.Meanwhile,lacZreporterfusionsusingpCM-lacZshowedthattheexpressionofphoBRandaioBAwerebothinducedbyAs(III)butwerenotinducedinHAL1-phoR931andHAL1-△phoB.Using15consensusPhoboxsequences,aputativePhoboxwasfoundintheaioBAregulationregion.PhoBwasabletobindtotheputativePhoboxinvivo(bacterialone-hybriddetection)andinvitro(electrophoreticmobilitygelshiftassay),andan18-bpbindingsequencecontainingnineconservedbasesweredetermined.ThisstudyprovidedtheevidencethatPhoBRregulatestheexpressionofaioBAinHalomonassp.HAL1underlowPicondition.ThenewregulationmodelfurtherimpliestheclosemetabolicconnectionbetweenAsandPi



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