微生物对人类健康有很大的影响.docx

微生物对人类健康有很大的影响.docx

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微生物对人类健康有很大的影响

IntroductiontoMicrobiology

Microbeshavealargeimpactonhumanhealth

（微生物對人類健康有很大的影響）

※Microbescausemanyinfectiousdiseases.（微生物導致許多傳染病）

※Vaccines,antibiotics,andmanyotheradvanceshavelessenedtheimpactofinfectiousdiseaseinthedevelopedworld,butinfectiousdiseaseindevelopingcountriesishigh.

（疫苗、抗生素以及許多其他的進步降低了傳染病對開發中地區的衝擊，但是發生在開發中國家的傳染病仍然偏高）

※Newillnessescausedbymicroorganismscontinuetoemergeandknownpathogensarebecomingresistanttotreatment.

（微生物所導致的新疾病持續出現，而且已知有許多病原體逐漸對醫療處理產生抗性）

In1900intheUnitedStatestheinfantmortalityratewasnear50%,mostlyduetochildhoodinfectiousdiseaseanduntilabout1930,microbeswerethemajorcauseofdeathinhumans.Fromtoday’sperspectivethisisahorrendous（可怕的）statistic（統計量）,overhalfofallinfantsdidnotmakeittoadulthood!

Withtheadventofantibiotics,vaccinesandbetterwatersanitation,humanityhasreducedtheimpactofpathogenicmicrobesindevelopedcountries,buttheywillalwaysremainanimportantsocialconcern.Thedisciplineofmicrobiologyemergedfromthestudyofthesediseases,andmostadvancesintreatingvariousailmentshadtheirrootsinthisrelativelyyoungscience.

"Ancient"diseasescontinuetobeaproblemwherenutritionandsanitationarepoor,andemergingdiseasessuchasAcquiredImmunodeficiencySyndrome（AIDS）areevenmoredangerousforsuchpopulations.TheCentersforDiseaseControlandPrevention（theU.S.governmentagencychargedwithprotectingthehealthandsafetyofpeople）estimatesthatabout9%ofadultsbetweentheagesof18-49inSub-SaharanAfricaareinfectedwithHIV.

Yet,AIDSisonlyoneofanumberofnewdiseasesthathaveemerged.Manyofthesediseaseshavenoknowncure.InfluenzaandpneumoniaareleadingkillersoftheelderlyevenintheU.S.andotherdevelopednations.Eventhecommoncoldcausesillnessandmiseryforalmosteveryoneanddrainstheproductivityofallnations.Manyofthenewdiseasesareviralinnature,makingthemnotoriouslydifficulttotreat.

Surprisingly,manydiseasesthatwerepreviouslythoughttohaveonlybehavioralorgeneticcomponentshavebeenfoundtoinvolvemicroorganisms.Theclearestcaseisthatofulcers,whichwaslongthoughttobecausedbystressandpoordiet.Howeverthecausativeagentisactuallyabacterium,Helicobacterpylori,andmanyulcerscanbecuredwithappropriateantibiotics.Workonothernon-infectiousdiseasessuchasheartdisease,strokeandsomeautoimmunediseasesalsosuggestamicrobialcomponentthattriggerstheillness.

Finally,somepathogenicmicrobesthathadbeen"controlled"throughtheuseofantibioticsarebeginningtodevelopdrugresistanceandthereforereemergeasseriousthreatsintheindustrializedworldaswellasdevelopingnations.Tuberculosisisanillnessthatwasonthedeclineuntilthemiddle80’s.Ithasrecentlybecomemoreofaproblem,partlyduetodrugresistanceandpartlyduetoahigherpopulationofimmunosuppressedindividualsfromtheAIDSepidemic.Staphylococcusaureusstrainsareemergingthatareresistanttomanyoftheantibioticsthatwerepreviouslyeffectiveagainstthem.Thesestaphinfectionsareofgreatconcerninhospitalsettingsaroundtheworld.Understandingbothfamiliarkillersandnewpathogenswillrequireanunderstandingoftheirbiology,andthusanunderstandingofthefieldofmicrobiology.

Microbesareoftenhelpful,notharmful

（微生物經常是有益而非有害的）

※Microbesformimportantmutualisticrelationshipswithallsortsoforganisms.Manyoftheserelationshipsareimportantfromahumanperspective

（微生物與許多生物形成重要的互利關係，而自人類角度而言其中有許多是很重要的關係）

Onlyasmallfactionofmicrobesareinvolvedindisease;manyothermicrobesactuallyenhanceourwell-being.Theharmlessmicrobesthatliveinourintestinesandonourskinactuallyhelpusfightoffdisease.Theyactivelyantagonizeotherbacteriaandtakeupspace,preventingpotentialpathogensfromgainingafootholdonourbodies.Indeed,likealllargeorganisms,humanshaveentirecommunitiesofmicroorganismsintheirdigestivesystemsthatcontributetotheiroverallhealth.Themicrobialcommunityinhumansnotonlyprotectsusfromdisease,butalsoprovidesneededvitamins,suchasB12.

Humanhealthandnutritiondependsonhealthyfarmanimals.Cows,sheep,horsesandotherruminantanimalsutilizetheirmicrobialassociatestodegradeplantmaterialintousefulnutrients.Withoutthesebacteriainsideruminants,growthonplantmaterialwouldbeimpossible.

Commercialcropsarealsocentraltohumanprosperity,andmuchofagriculturedependsupontheactivitiesofmicrobes.Forexample,anentiregroupofplants,thelegumes,formsacooperativerelationshipwithcertainbacteria.Thesebacteriaformamutualisticrelationshipwithintheplant:

theplantprovidescarbonandenergy,whilethebacteriaconvertatmosphericnitrogengasintoausefulnitrogensourcefortheplant.

Microbesalsoserveassmallfactories,producingvaluableproductssuchascheese,yogurt,beer,wine,organicacidsandmanyotheritems.Inconclusion,whileitislessapparenttous,thepositiveroleofmicrobesinhumanhealthisatleastasimportantasthenegativeimpactofpathogens.

Microbeshaveprofoundeffectsontheenvironment

（微生物對環境有深遠的影響作用）

※MicrobesmakeupthemajorportionofthebiomasspresentontheEarth.Therefore,thenutrientstheyeatandtheproductstheyformgreatlyinfluencetheenvironment.

（微生物是現存地球上生物質量的主要組成份子，因此，它們所吃掉的養分以及它們所形成的產物對環境有巨大的影響）

※Cyanobacteriaandalgaeintheoceansareresponsibleformostphotosynthesisandareamajorsinkforcarbondioxide,agreenhousegas.

（存在海水中的藍綠菌和藻類是大部份光合作用的來源，也是主要的溫室效應氣體-二氧化碳的收集處）

※Microbesreleasenutrientsfromdeadorganisms,makingthemavailabletotherestoftheecosystem.

（微生物將養分自死亡的生物體釋放出來，提供給生態系中其餘生物所利用）

※Somemicrobesplayaroleintheproductionofenergy,whileothermicrobesinterferewithenergyproduction.

（部份微生物在能量的產生中扮演一角，其餘的微生物則妨礙能量的產生）

Whethermeasuredbythenumberoforganismsorbytotalmass,thevastmajorityoflifeonthisplanetismicroscopic.Theseteamingmultitudesprofoundlyinfluencethemake-upandcharacteroftheenvironmentinwhichwelive.Presently,weknowverylittleaboutthemicrobesthatliveintheworldaroundusbecauselessthan2%ofthemcanbegrowninthelaboratory.Understandingwhichmicrobesareineachecologicalnicheandwhattheyaredoingthereiscriticalforourunderstandingoftheworld.

Microbesarethemajoractorsinthesynthesisanddegradationofallsortsofimportantmoleculesinenvironments.CyanobacteriaandalgaeintheoceansareresponsibleforthemajorityofphotosynthesisonEarth.Theyaretheultimatesourceoffoodformostoceancreatures（includingwhales）andreplenishtheworld’soxygensupply.Cyanobacteriaalsousecarbondioxidetosynthesizealloftheirbiologicalmoleculesandthusremoveitfromtheatmosphere.Sincecarbondioxideisamajorgreenhousegas,itsremovalbycyanobacteriaaffectstheglobalcarbondioxidebalanceandmaybeanimportantmitigatingfactoringlobalwarming.

Inallhabitats,microorganismsmakenutrientsavailableforthefuturegrowthofotherlivingthingsbydegradingdeadorganisms.Microbesarealsoessentialintreatingthelargevolumeofsewageandwastewaterproducedbymetropolitanareas,recyclingitintocleanwaterthatcanbesafelydischargedintotheenvironment.Lesshelpfully（fromtheviewofmosthumans）,termitescontainmicroorganismsintheirgutsthatassistinthedigestionofwood,allowingthetermitestoextractnutrientsfromwhatwouldotherwisebeindigestible.Understandingofthesesystemshelpsustomanagethemresponsiblyandaswelearnmorewewillbecomeevermoreeffectivestewards.

Energyisessentialforourindustrialsocietyandmicrobesareimportantplayersinitsproduction.Asignificantportionofnaturalgascomesfromthepastactionofmethanogens（methane-producingbacteria）.Numerousbacteriaarealsocapableofrapidlydegradingoilinthepresenceofairandspecialprecautionshavetobetakenduringthedrilling,transportandstorageofoiltominimizetheirimpact.Inthefuture,microbesmayfindutilityinthedirectproductionofenergy.Forexample,manylandfillsandsewagetreatmentplantscapturethemethaneproducedbymethanogenstopowerturbinesthatproduceelectricity.Excessgrain,cropwasteandanimalwastecanbeusedasnutrientsformicrobesthatfermentthisbiomassintomethanolorethanol.Thesebiofuelsarepresentlyaddedtogasolineandthusdecreasingpollution.Theymayone-daypowerfuelcellsinourcars,causinglittlepollutionandhavingwaterastheironlyemission.

Finally,Weareincreasinglytakingadvantageoftheversatileappetiteofbacteriatocleanupenvironmentsthatwehavecontaminatedwithcrudeoil,polycholorinatedbiphenvyls（PCBs）andmanyotherindustrialwastes.Thisprocessistermedbioremediationandisacheapandincreasinglyeffectivewayofcleaninguppollution.

Studyingmicrobeshelpsustounderstandtheworldaroundus

（研究微生物協助我們瞭解在我們周遭的世界）

※Microbesareusefultoolsinresearchbecauseoftheirrapidlifecycle,theirsimplegrowthrequirements,andtheirsmallsize.

（由於快速的生活史、簡單的生長需求與渺小的體型，微生物是有用的研究工具）

※Duetothissimplicity,microbeshavebeenessentialinunderstandingcorequestionsinbiology.

（由於它簡單的結構，微生物一直是生物學中瞭解核心問題所不可缺的）

※Attemptstoclassifymicroorganismshaveleadtoaclassificationsystemthatdividesallorganismsintothreedomainsoflife,Archaea,Bacteria,andEukarya

（試圖分類微生物也導致生物分類系統的形成，將所有生物分為原生菌、細菌、真核生物三大領域）

※Microbesprovidetoolsforuseinmolecularbiology.Thesetoolshaveallowedscientiststomakerapidprogressininvestigatingmanytypesofmicroor