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1、Chapter1-TheRelevanceandHistoryofMicrobiology1-1IntroductionThisbookwillfocusonthebiologyofsmallthings,butwhatismicrobiology?Microbiologycouldbedefinedasthestudyoforganismstoosmalltobeseenwiththenakedeye.Figure1-14showstherelativesizeofmicrobescompared
2、tootherlivingthings.However,therecentdiscoveryofbacteriaofnear1mminsizehasmadethisdefinitionsomewhatinaccurateandinthegrandtraditionofscience,anewdefinitionisinorder.Figure1-14TherelativesizeofmicrobesThoughmicrobesaresmall,theyneverthelessspanalargera
3、ngeofsizesfromthesmallestbacterialcellsat~0.15µmtogiantbacterialargerthan700µm.Thevirusesdepictedatthefarleftofthescaleareevensmaller.Wewillconsidermicrobiologytobethestudyoforganismsthatcanexistassinglecells,containanucleicacidgenomeforatleastsomepart
4、oftheirlifecycle,andarecapableofreplicatingthatgenome.Thisbroaddescriptionencompassesanunderstandablylargegroupoforganismsincludingfungi,algae,protozoaandbacteria.ExamplesoftheseareshowninFigure1-15.Thisdefinitionwouldalsoincludeviruses,whichmicrobiolo
5、gytextstraditionallydiscussalongwithlivingorganisms.Figure1-15SomeexamplesofthetypesofmicrobespresentintheenvironmentManydifferentorganismsfallunderthedefinitionofmicroorganisms.Shownhereare:A,thebacteriumEscherichiacoli;B,aphotosyntheticcyanobacterium
6、;C,afungus;D,Ebolavirus;E,theprotozoanmalariaparasite.(Sources:B,MikeClayton;C-E,CDC).Notethatthescaleoneachofthesepicturesisdifferent.Microbiologyalsoinvolvesacollectionoftechniquestostudyandmanipulatethesesmallcreatures.Becauseoftheirsize,specialinst
7、rumentsandmethodshadtobedevelopedtoallowtheperformanceofinterpretableexperimentsonmicroorganisms.Thesemethodsarenotrestrictedtomicrobesalone,buthavealsofoundutilityinworkingwithpopulationsofcellsfromhigherorganisms.Withapologiestoothersmallorganisms,th
8、isbookwillmostlyfocusonbacteria(whichwewillalsocallmicroorganismsormicrobes)andtheirimpactontherestofthebiosphere.Thiscanbeweaklyjustifiedbythefactthatbacteriahaveamajorimpactontheworldaroundusand,becauseoftheirperceivedimportance,morer
