human-hair-the-bronx-high-school-of-science：人的頭發(fā)的布朗克斯科學(xué)高中課件

AIM:Howdowepreparespecimenforobservationusingacompoundlightmicroscope?INGROUPS:

Howwouldyouprepareaslidetoobserveprotists(e.g.paramecia,amoeba,etc)usingamicroscope??

HINT:YoudidthisinRegentsBiology!WetMountUsedtoobservelivingorganismAdropofbrothwiththeorganismisplacedontheslideorAdropofwaterisplacedontheslideandasampleofbacteriafromagarisadded2%carboxymethylcelluloseslowsthemdown(ifmobile)Howelsemightascientistpreparespecimenforobservationusingamicroscope?SmearsonaSlideUsedtoviewkilledorganismsOrganismsarelivingwhenplacedontheslidebutthepreparationtechniqueskillthemSmearProcedureSterilizeloop&placeloopfulofwateroneachslideifcultureisfromagarslant.FlameloopAllowtocoolRemovecapfromtesttube&flamemouthTouchlooptoculture&removebacteriaFlametesttube&replacecapSpreadbacteriainwateronslideMakethinfilmAllowtheslidetoairdry.FixBacteriatoSlideAfterdry,passthroughflame–filmsideup–aboutthreetimes-andtouchbottom–shouldfeeljustwarmWhyfixbacteriatoaslide?WhyFixBacteriatoSlide?PreventswashingoffduringstainingBacteriacontainalbumins,atypeofmateriallikeblood,whichcausesthemtoclingtotheglassslideCulturesusedare24hoursoldPreventsdistortionofcellsAnalyzetheprocedureformakingsmearsanddiscusspossibletechnicalpitfalls.ProblemswithaSmearToothick–can’tseethroughToothin–can’tfindanyorganismsPreparationmaydisruptstructuralchainsorotherarrangementsToomuchheatfixingmaydestroyorganismsbeyondobservationHintsforPreparing

BacterialSmearsUsecleanslidesWashwithsoapandwaterToweldry–polishFlamesidetobeusedtoremovegreaseHandleonlyonedgesThoughitmayseemtrivial,whyislabelingarguablythemostimportanttaskinsmearpreparation.LabelSlideMakeacircleoneachslidethesizeofadimeusingawaxpencilIncludeGroupnamesanddateLabeleachslideintheupperleftExampleEc=EscherichiacoliBs=BacillussubtilisSl=SarcinialuteaAfterpreparingthebacterialsmear,whyshouldamicrobiologiststainbacteria?WhyStainBacteria?

Unstainedbacteriaaretransparentwiththelightmicroscope.Stainingaidsintheidentificationofbacteria.Bacterialstainsaremadefromsyntheticdyes.PrinciplesofStaining

Astainordyeisasaltcomposedofapositiveandnegativeion.Oneionhascolorandiscalledthechromophore.InGroups:

Identifypossiblebacterialstructuresthatcanbetargetedforstaining.BacterialCellularStructures

toStainCellMembraneCellWallFig.4-3AnOverviewofStructureBasicDyesPositivelychargedionhascolor.Goodforbacterialcellmembraneswhicharenegativelychargedataphof7.Examples:MethyleneblueCrystalvioletSafraninMalachitegreenMorecommonlyusedthanacidicdyes.AcidicDyesNegativelychargedionhascolorRepelledbynegativelychargedbacterialmembranesUsedfornegativestainingtoseeshape,sizeandcapsulesExamplesEosinNigrosinTypesofStainsSimpleorDifferentialSimpleStainsSingledyeRevealsbasiccellshapesandarrangementsExamples

MethyleneblueSafraninCarbolfuchsinGentianvioletDifferentialStainUsestwoormoredyesDistinguishesbetweentwokindsoforganismsortwopartsofanorganismExamplesGramstain(mostfrequentlyused)Ziehl-NielsenAcidFastStain(vividredcolor)ForleprosyandTBSchaeffer-FultonsporestainASimpleStainE.coli -Eosin(Red) - 2minutes orCarbolfuchsin- 30secondsS.lutea -MethyleneBlue- 2minutesB.subtilis-CrystalViolet - 3