极端环境微生物

S12|NATURE|VOL495|14MARCH2013BYPETERGWYNNETakeasolutionofgoldchloride,acom-poundtoxictomostformsoflife.AddacolonyofCupriavidusmetallidurans,oneofthefewbacteriaabletosurviveamidcompoundsofheavymetalsinminesacrosstheworld.Asthebacteriaaccumulatethegoldsaltfromthesolution,biochemicalpro-cesseswithintheorganismsreduceittothepuremetal,whichthebacteriaexcreteintheformoftinygoldnuggets—nanoparticlesofpuregold.Thebacteriaproducethegoldasprotectionfromthetoxicgoldcomplexesthatwouldotherwisedestroytheircells.Theprocesswon’tinspireanewgoldrush,becausescalingitupwouldbebothprohibi-tivelyexpensiveandtime-consuming,butitdoeshaveimplicationsforthecreation,detec-tionandprocessingofthisnoblemetal.Anditallreliesonextremophilemicroorganismsthatcanthriveinenvironmentsrichinsolutionsofsaltsthatarelethaltomostformsoflife.Recentfindingsmayleadtobioindicatorsthatcanidentifymicroorganismsassociatedwithgoldandhencepinpointthepresenceofthemetal;biosensorsthatcanhelpprospectingteamsquicklydeterminetheconcentrationofgoldinenvironmentalsamples;andthebiosyn-thesisofgoldnanoparticles,whichhavepoten-tialapplicationsinoptoelectronics,imagingtechnology,catalysis,drugdeliveryandmore.Researchersarealsoexploringwhetherbacteriaplayedaroleinthecreationofgolddepositsworldwide.Deeperunderstandingofthelinkbetweenbacteriaandgoldcouldevenleadtobacteriaproducingcustomizedgoldnuggets.Thereareeconomic,environmentalandsci-entificreasonsforthecurrentinterestintheconnectionbetweenbacteriaandgold.Thepriceofgoldhasrisenbyafactorof4.5duringthepastdecade(see‘Mine,allmine!’,pageS2).Thisleaphasmadegoldmininghighlyprofit-able.“Butitalsomeansthatnewdepositshavetobefoundanddifficulttypesoforehavetobeprocessed,”saysFrankReith,ageomicrobiol-ogistattheUniversityofAdelaideinAustralia.MICROBIALALCHEMISTSCertainbacteriaare“microbialalchemists,transforminggoldfromsomethingthathasnovaluetoasolid,preciousmetal”,accordingtoKazemKashefi,amicrobiologistandmolecu-largeneticistatMichiganStateUniversityinEastLansing.“Formillionsofyearsthey