Mushroomsmayturnouttobeimportantkeystobothhumanhealthandplanetaryhealth.Theirindispensableroleinrecyclingorganicmatter,especiallyinforests,haslongbeenknown.Buthowmanypeoplerealizethattreesandothergreenplantscouldnotgrowandreachmaturitywithoutsymbioticassociationswithmushrooms,atleastwithmyceliumThenetworkoffungalthreadsinsoilthatactasinterfacesbetweenplantrootsandnutrients?菌絲體(mycelium)：由許多菌絲連結在一起組成的營養(yǎng)體叫菌絲體。Amushroomisthereproductivestructureorfruitingbodyofmycelium.Myceliumrunsthroughourworld,butitishiddenandinconspicuous---astrangelifeformthat

hasnotattractedthesamescientificattentionasmicro-organismsorplantsoranimals.WhyWesternmedicinehadneverlookedtomushroomsassourcesofnewtherapeuticagents,giventheirprominenceinthetraditionalpharmacopeiasofChina,Japan,andKorea.Thenaturalcompetitionthatexistsinsoilbetweenmyceliumandbacteria.Fungihaveevolvednovelchemicaldefenses,arangeofantibioticsthatareoftenactiveagainstnotonlybacteriabutalsovirusesandotherinfectiousagentsthatcausediseaseinhumans.Fungi,especiallyfungifromold-growthforests,maybesourcesofnewmedicinesthatareactiveagainstarangeofgerms,includingHIV/AIDSandthecausativeagentsofsmallpoxandanthrax,potentialbioterroristthreats.Myceliumcanbeselectedandtrainedtobreakdowntoxicwaste,reducingittoharmlessmetabolites.Mycoremediation

Hehasdemonstrateditspracticalityincleaningupoilspills.Hesuggeststhatourmushroomalliesmayevenbeabletodetoxifychemicalwarfareagents.

Therearemorespeciesoffungi,bacteria,andprotozoainasinglescoopofsoilthantherearespeciesofplantsandvertebrateanimalsinallofNorthAmerica.

TheHistoryofFungalNetworksAnimalsaremorecloselyrelatedtofungithantoanyotherkingdom.Morethan600millionyearsagowesharedacommonancestry.

Fungievolvedameansofexternallydigestingfoodbysecretingacidsandenzymesintotheirimmediateenvironmentsandthenabsorbingnutrientsusingnetlikecellchains.Fungimarchedontolandmorethanabillionyearsago.Manyfungipartneredwithplants,whichlargely

lackedthesedigestivejuices.Mycologistsbelievethatthisallianceallowedplantstoinhabitlandaround700millionyearsago.Manymillionsofyearslater,

oneevolutionarybranchoffungiledtothedevelopmentofanimals.

TheMycelialArchetypeThesimilarityinformtomyceliummaynot

bemerelyacoincidence.mostenergy-conservingforms

maximizethepoolingofdataandcomputationalpowerwhileminimizingcriticalpointsuponwhichthesystemisdependentInternetissimplyanarchetypalform,theinevitableconsequenceofapreviouslyprovenevolutionarymodel,whichisalsoseeninthehumanbrain.MyceliumintheWebofLifeYear-round,fungidecomposeandrecycleplantdebris,filtermicrobesandsedimentsfromrunoff,andrestoresoil.Intheend,life-sustainingsoiliscreatedfromdebris,particularlydeadwood.Whilemyceliumnourishesplants,mushroomsthemselvesarenourishmentforworms,insects,mammals,bacteria,andother,parasiticfungi.Ibelievethattheoccurrenceanddecompositionofamushroompre-determinesthenatureandcompositionofdown-streampopulationsinitshabitatniche.Allhabitatsdependdirectlyonthesefungalallies,withoutwhichthelife-supportsystemoftheEarthwouldsooncollapse.Inthe1960s,theconceptof“betterlivingthroughchemistry”becametheidealasplastics,alloys,pesticides,fungicides,andpetrochemicalswereborninthelaboratory.

Whenthesesyntheticswerereleasedintonature,theyoftenhadadramaticandinitiallydesirableeffectontheirtargets.Toxicfungicideslikemethylbromide,oncetouted,notonlyharmtargetedspeciesbutalso

nontargetedorganisms.Toxicinsecticidesoftenconferatemporarysolutionuntiltoleranceisachieved.Whenthenaturalbenefitsoffungihavebeen

repressed,theperceivedneedforartificialfertilizersincreases,creatingacycleofchemical

dependence,ultimatelyerodingsustainability.Ourrelativelysuddenriseasa

destructivespeciesisstressingthefungalrecyclingsystemsofnature.Thecascadeoftoxinsanddebrisgeneratedbyhumansdestabilizesnutrientreturncycles,causingcropfailure,globalwarming,climatechangeand,inaworst-casescenario,quickeningthepacetowardsecocatastrophesofourownmaking.Ibelievewecancomeintobalancewithnatureusingmyceliumtoregulatethe

flowofnutrients.

Mushroomsreproducethroughmicroscopicspores,visibleasdustwhentheycollectenmasse.Whenthemoisture,temperature,andnutrientsareright,sporesfreedfromamushroom(essentially

mushroomseeds),germinateintothreadsofcellscalledhyphae.Aseachhyphagrowsandbranches,itformsconnectionswithotherhyphaefromcompatiblesporestocreateamycelialmat,whichmatures,gatheringnutrientsandmoisture.Frommycelium,cellsaggregatetoformaprimordium-

called“pinheads”orbabymushroomsbygrowers.Underoptimalconditions,thetransformationfromsporestomyceliumtomushroomcantakejustafewdays.Mushroomscanbeplacedin4basiccategories:saprophytic,parasitic,mycorrhizal,andendophytic,dependinguponhowtheynourishthemselves.Nowlet’stakeashorttourthroughthe4majorcategoriesofmushrooms.

SaprophyticMushrooms:TheDecomposersSaprophyticmushrooms,thepremierrecyclersontheplanet;buildingsoilsistheprimaryoutcomeoftheactivitiesofthesesaprophyticfungi,whosefilamentousmycelialnetworksweavethroughandbetweenthecellwallsofplants.Whenorganicmatterfallsfromthecanopyoftreesandplantsoverheadontotheforestfloor,thedecomposersresidinginthesoilprocessthisnewlyavailablefood.

Thesefungisecreteenzymesand

acidsthatdegradelargemoleculesofdeadplantsintosimplermolecules,whichthefungicanreassembleintobuildingblocks,suchaspolysaccharides,forcellwalls.Fromdeadplants,fungirecyclecarbon,hydrogen,nitrogen,phosporus,andmineralsintonutrientsforlivingplants,insects,

andotherorganismssharingthathabitat.

Asdecomposers,saprophyticmushroomscanbeseparatedinto3keygroups:primary,secondary,andtertiary

PrimaryDecomposersThesesaprophytesaretypicallythefirsttogrowonatwig,abladeofgrass,achipofwood,alog,astump,oradeadinsectorotheranimal.Primarydecomposersaretypicallyfastgrowing,sendingoutrapidlyextendingstrandsofmyceliumthatquicklyattachtoanddecomposeplanttissue.

SecondaryDecomposersSecondarydecomposersrelyontheactivityofprimaryfungithatinitially,althoughpartially,breakdownplantandanimaltissues.Secondarydecomposersallworkinconcertwithactinomycetes,otherbacteria,andfungi,includingyeasts,insoilintheforestfloororincompostpiles.

Cultivatorsexploitthissequencetogrowthewhitebuttonmushroom(Agaricusbisporus),themostwidelycultivatedmushroomintheworld.TertiaryDecomposersThedivisionbetweensecondaryandtertiarydecomposersisoftenobscure;Thisdifficult-to-categorizegroupincludesfungifoundtowardtheendofthedecompositionprocess.Theythriveinhabitatscreatedbyprimaryandsecondarydecomposersoveraperiodofyears,oftenpoppingupfromsoilsholdinglittledecomposablematerial.ParasiticMushrooms:BlightsoftheForestorAgentsforHabitatRestoration?Parasitesarepredatorsthatendangerthehost’shealth.Inthepast,foresterssawallparasiticfungias

hostiletothelong-termhealthofforests.Althoughtheydoparasitizetrees,theynourishotherorganisms.

Parasiticfungisuchasthehoneymushroom,whichcandestroythousandsofacresof

forest,arestigmatizedasblights.

However,moreforestersarerealizingthatarottingtreeinthemidstofacanopiedforestis,infact,moresupportiveofbiodiversitythanalivingtree.Parasiticmushroomsmaybenature’swayofselectingthestrongestplantsandrepairingdamagedhabitats.

Eachtimethisfungusblightsweepsthrough,nurselogsarecreated,soildepthincreases,andcentimetersofsoilaccumulatetocreateever-richerhabitatswhereonceonlybarrenrockstood.

MycorrhizalMushrooms:FungusandPlantPartnershipsMycorrhizalmushrooms(mycomeans“mushroom”;rhizalmeans“relatedtoroots”),formmutuallybeneficialrelationshipswith

plants.Infact,mostplantsfromgrassestoDouglasfirshavemycorrhizalpartners.

Themyceliaoffungalspeciesthatformexteriorsheathsaroundtherootsofpartnerplantsaretermedectomycorrhizal.Themycorrhizalfungithatinvadetheinteriorrootcellsofhostplantsarelabeledendomycorrhizal.Bothplantandmycorrhizaebenefitfromthisassociation.

Becauseectomycorrhizalmyceliumgrowsbeyondtheplant’sroots,itbringsdistantnutrientsandmoisturetothehostplant,extendingtheabsorptionzonewellbeyondtherootstructure.Themyceliumdramaticallyincreasestheplant’singestionofnutrients,nitrogenouscompounds,andessentialelements(phosphorus,copper,andzinc)asitdecomposessurroundingdebris.

DavidPerry(1994)postulatesthatthesurfacearea—henceitsabsorptioncapability—ofmycorrhizalfungimaybe10to

100timesgreaterthanthesurfaceareaofleavesinaforest.Plantswithmycorrhizalfungalpartnerscanalsoresistdiseasesfarbetterthanthose

without.

Fungibenefitfromtherelationshipbecauseitgivesthemaccesstoplant-secretedsugars,

mostlyhexosesthatthefungiconverttomannitols,arabitols,anderythritols.

Oneofthemostexcitingdiscoveriesinthefieldofmycologyisthatthemycorrhizaecantransportnutrientstotreesofdifferentspecies.Onemushroomspeciescanconnectmanyacresofaforestinacontinuousnetworkofcells.

Inoneexperiment,researcherscomparedtheflowofnutrientsviathemyceliumbetween3trees:aDouglasfir,apaperbirch,andawesternredcedar.TheDouglasfirandpaperbirchsharedthesameectomycorrhiza,whilethecedarhadanendomycorrhiza.TheresearcherscoveredtheDouglas

firtosimulatedeepshade,thusloweringthetree’sabilitytophotosynthesizesugars.Inresponse,themycorrhizaechanneledsugars,trackedbyradioactivecarbon,fromtherootzoneofthebirchtotherootzoneofthefir.Morethan9percentofthenetcarboncompoundstransferredtothefiroriginated

fromthebirch’sroots,whilethecedarreceivedonlyasmallfraction.Theamountofsugartransferred

wasdirectlyproportionaltotheamountofshading(Simardetal.1997).

AnearlierstudybyKristina

Arnebrantandothers(1993)showedasimilarbidirectionaltransferofnitrogen-basednutrientsfromalder(Alnusglutinosa)topine(Pinuscontorta)throughasharedectomycorrhizalmycelium.

acommonmycelialnetcouldunite3speciesoftreesandunderscoredaremarkableabilityofmycorrhizalfungi:mycorrhizaecankeepdiversespeciesoftreesinforestsfed,particularlyyoungertreesstrugglingforsunlight.Nowwehaveabetterunderstanding

ofhowsaplingssurviveintheshadowsofeldertreesthattoweroverheadandblockoutessentiallight.

MutualisticSpecies:FungalPartnershipsMutualismoccurswhen2ormoreorganismsworkdirectlytogetherfortheirmutualbenefit,usuallytopreventinfestationbyparasitesandgathernutrients.Manyorganisms,fromplantstoants,seekfungiasprotectors,andviceversa.Thisrapidlyexpandingfieldofstudyisoneofthemostexcitinginmycology.InsectsandMushroomsManyinsectsusemushroomsasplatformsforincubatingandfeedingtheirlarvae.

Oneofthefirstcasesofmutualismtobenoticedwastheinterrelationshipbetweenmushroomsandtermites.ThemushroomgenusTermitomycesincludesseveralspeciesofmushroomsassociatedwithterrestrialtermitecolonies,especiallyinthetropics.Termitesconstructtheirnestswithorganicmatterandcultivatemycelium.Whenabandoned,thesemycelium-richnestssproutdeliciousmushrooms.

Sincecertainfungifunctionasnaturalbactericidesandfungicides,someinsectsengagethemasalliesinanefforttocounterinfectionsfromhostilebacteriaandotherfungi.

StudiesatOregonStateUniversity(Currieetal.2003)showthatattineants,grow

Lepiotamyceliumasahostforabenignfungusthatproducesanantibioticagainstdestructivemicrofungalparasites(Escovopsissp.),andtheyalsofeedLepiotamyceliumtotheirlarvae.

SnailsandslugslovemushroomsSomesnailsenlistfungitohelpthemdigestplants.SillimanandNewell(2003)foundthataseasidesnail,themarshperiwinkle(Littorariairrorata),damagesandthendefecatesoncertaingrass(Spartinaalternifolia),whereaparticularfungussoongrows.Dayslater,thesnailsreturntothegrass,nowovergrowingwithfungus,andconsumebothfungusandplant.Endophytes:MutualisticSymbiontsEndophytesareprimarilybenevolent,nonmycorrhizalfungithatpartnerwithmanyplants,fromgrassestotrees.Theirmyceliathreadbetweencellwallsbutdon’tenterthem,enhancingaplant’sgrowthandabilitytoabsorbnutrients,whilestavingoffparasites,infections,andpredationfrom

insects,otherfungi,andherbivores.

Endophyticfungiareespeciallyskilledatproducingspecializedtoxiccompounds.Endophytesinlargecrabgrass,forexample,appeartoproducetoxinsthatkillfireants,andthoseingrassessuchasthedarnelweed(Loliumtemulentum)causesleepinessincattleandhorses,afactlongknowntoranchersinCentralAmerica.

Endophytes,whichwereoncethoughttobepathogens,areincreasinglyviewedas

engagingtheplantinamutuallybeneficialrelationship.Ina2003experimentinPanama,researchers

foundthatwhenendophyte-freeleavesfromthechocolate-producingcocoatree(Theobromacacao)wereinoculatedwithendophytes,leafnecrosisandmortalitydeclinedthreefold,suggestingabiodefensiveeffectispossibleagainstotherpathogens.Accordingtooneestimate,morethan10,000sporesoffungilandoneachleafperday.Sporesfromendophytescompetewithmanyotherfree-flyingfungalspores.Amidstsuchcompetition,friendlyfungitakingupresidenceisactuallyanassettoplantsotherwisesubjecttopathogenicassault.WheatfarmersbenefitfromtheendophytePiriformosporaindica.Thisspeciesisaroot-basedendophytethatpromotesthegrowthofwheatshootsandrootsandiscapableofincreasingleafandseedproduc