Hands-on Activity
Winogradsky Columns: Microbial
Ecology in the Classroom
Educator Materials
WINDOGRADSKYCOLUMNS:MICROBIALECOLOGYINTHECLASSROOM
OVERVIEW
Thisactivitycomplementsthe2012HolidayLecturesonScience,“ChangingPlanet:Past,Present,
Future.”Winogradskycolumnsprovideavisualexampleofvariousmodesofmetabolisminthe
microbialworld.Ittakesapproximately6to8weekstoseelayersofmicrobialgrowth,butthe
experimentcanbeconductedforalongertimeperiod.
KEYCONCEPTSANDLEARNINGOBJECTIVES
•
Microbeshaveawidevarietyofmetaboliccapabilities,manyexamplesofwhichcanbefound
inagenericsamplefromtheenvironment.
•
Acombinationofmicrobialmetabolismandphysicalparameters(suchaslightavailabilityand
diffusion)leadtoecosystemstratification.
•
Themetabolicrequirementsofonegroupoforganismscanbeprovidedbythebyproductsof
anothergroup.
•
Whiledifferentmicrobesareadaptedtodifferentecologicalniches,theyalsoplayarolein
formingthoseniches.
•
Microbesplayaroleinelementalcycling.
Studentswilllearn
•
HowtobuildaWinogradskycolumn.
•
Makeobservationsonanongoingexperiment.
TIMEREQUIREMENTS
Theactivitytakes6to8weekstocomplete.Itwilltakeacoupleofhoursforstudentstogetsamples
andsetuptheexperiment,butthentheywillneedtorecordobservationsforafewminutesaboutonce
aweek.
SUGGESTEDAUDIENCE
Thisactivitycanbeusedinhigh-schoolbiology(alllevelsincludingAPandIB),environmentalscience,
andmicrobiologyclasses.
MATERIALS
•
•
•
•
•
•
4clear,16-oz.plasticbottles.Largercontainerswillalsowork;adjustthesedimentvolumes
accordingly.
1–4disposablecontainers(e.g.,plasticstoragecontainerorplasticbaggie)formixingsediment
1trowelfordiggingasedimentsample
Permanentmarker
4smalllabels(1foreachbottle)
Water
www.BioInteractive.org
Published2013
Page1of3 Hands-on Activity
Winogradsky Columns: Microbial
Ecology in the Classroom
•
•
•
•
•
•
•
•
Educator Materials
1bucketorcontainerlargeenoughtohold6–10cupsofsediment Awell-litlocationwherethecolumnscansitundisturbedfor6–8weeks
Digitalcameraorcell-phonecamera
Largemeasuringcuporothercontainerformeasuringsedimentandmixture
Acarbonsource,shreddednewspaper;approximately1cuplooselypacked
6–10cupsofsediment(mud)
Asulfursource;raweggyolkisbestLargemixingspoon(optional)
1funnel(optional)Coloredpencils(optional)
ANSWERKEY
Duringthecourseoftheexperiment,spendsometimeconsideringthefollowingquestions.Someof
thesequestionsmayrequireextraresearch.Feelfreetoconsultamicrobiologytextbook(e.g.,tolearn
aboutthesulfurcycle).
1.Howdoyourcolumnsdiffer?Howaretheythesame?Explainthedifferencesyousee.
Answerswillvary.
2.Didyouobservechangesinthecontrolcolumn?Ifso,explainwhytheyoccurred.
Answerswillvary.Gradientsmayalsoformincontrolcolumnbecausetherearenaturalformsof
carbon,sulfur,andothernutrientsinthesediment.Allthesamemicrobialprocesseswilloccurbut
maybetoalesserextent(dependingonthesedimentsource).
3.Winogradskycolumnsformoxygenconcentrationgradients.Predictthedistributionofoxygen
throughoutthecolumn.(Considertheentirecolumn:thesediment,thewater,andtheair.)
Overtime,anoxygengradientdevelopsfromhighatthetoptocompletelyanoxic(nooxygen)atthe
bottomofthecolumn.Theoverlyingairhasthehighestoxygenconcentration,andtheconcentration
decreasesasyoumovedownthroughthewaterandsedimenttothebottomofthecolumn.
Extradetail:Whenthecolumnisprepared,oxygenisevenlydistributedthroughoutthecolumn.Itis
consumedbyrespirationthroughoutthecolumn,butitisonlyproducedinthephotosyntheticlayer
atthetop.Anyoxygenthatdiffusesdownintothesedimentfromthetopmostlayerreactswith
chemicalcompoundsintheanoxiclayer.
4.Winogradskycolumnsformsulfideconcentrationgradientsaswell.Inthecolumnsthatcontainegg
yolk,predicthowsulfidewillbedistributedthroughoutthecolumn.(Considertheentirecolumn:the
sediment,thewater,andtheair.)
Sulfidewillbehighestinthebottom(anoxic)partofthecolumnandwilldecreaseupward,withno
sulfideatthetopofthesedimentorintheoverlyingwater.Extradetail:Whenthecolumnis
prepared,sulfurwillbedistributedthroughoutthecolumnbymixing.Sulfurisconvertedtosulfideby
anaerobicrespiration,whichwillonlyoccurinthebottomofthecolumn.Anysulfidethatdiffuses
www.BioInteractive.org
Published2013
Page2of3 Hands-on Activity
Winogradsky Columns: Microbial
Ecology in the Classroom
Educator Materials
upwardwillreactwithoxygen(eitherabioticallyorthroughmicrobialmetabolism).
5.Sulfurreductionisaformofanaerobicrespiration.Desulfovibrioareanexampleofbacteriathat
reducesulfurasawayofrespiringintheabsenceofoxygenandreleasesulfide.Whereinthecolumns
wouldyouexpecttofindthem?
Desulfovibriowouldbefoundinthebottompartsofthecolumnswherethereisnooxygen.
6.Purplesulfurbacteriaandgreensulfurbacteriaaretwotypesofbacteriathatusesulfidetosupport
photosynthesis.Ingeneral,greensulfurbacteriatoleratehigherlevelsofsulfidethanpurplesulfur
bacteriado.Predictwherethegreenandpurplesulfurbacteriawouldbeinrelationtoeachother.Also
predictwhereinthecolumnthepurplesulfurbacteriawouldbeinrelationtotheDesulfovibriobacteria.
Purplesulfurbacteriawillbeconcentratedinalayerabovethegreensulfurbacteriabecausethatis
wherethereislesssulfide.Inaddition,boththegreenandpurplesulfurbacteriawillbelayered
abovetheDesulfovibriobacteria.Extradetail:SinceDesulfovibriocanreducesulfur,theyproduce
sulfidethatsupportsthemetabolismofgreenandpurplesulfurbacteria.However,Desulfovibriodo
notrequirelight,sotheywillbefoundlowerinthecolumn.
7.Ifsampleswereextractedfromthevariouslayersofallthecolumns,wherewouldyoufind
photosyntheticorganismssuchascyanobacteriaandalgae?Explainwhy.
Photosyntheticcyanobacteriaandalgaewillmostlikelybesampledfromthewateratthetopofeach
columnbecausetheyrequireonlywater,carbondioxide,andlight,whichismostintenseatthetopof
thecolumn(assuminganoverheadlightsource).
8.ExplainhowWinogradskycolumnsillustratethediversityofmicroorganismsfoundonEarthtodayin
termsofthediversityofnichestheyoccupy.
Differentlayersforminthecolumnbasedontheavailabilityofoxygenandothernutrients.Different
groupsoforganismsoccupyeachoftheselayers,buttheyallcamefromtheoriginalsample.This
illustratesthepointthatthereisarichdiversityoforganismsinverycommonenvironmentssuchas
yourbackyardstream.Furthermore,thegradientsthemselvesareaproductofmicrobialmetabolism.
Thisillustratesthatmicrobesdon’tjustadapttotheirenvironment;theirmetabolismsactuallycreate
chemicalnicheswiththeenvironment.
9.ExplainwhattheWinogradskycolumnsillustrateaboutlifeonearlyEarth.
Mostofthestratainthecolumnsareanoxic,yetlifeabounds.Similarly,Earth’searlyatmospherewasdevoidof
oxygen,butmicrofossilsandgeochemicalevidencesuggestthatlifewasubiquitous.Alargediversityof
microbesareadaptedtolifewithoutoxygen.
ExtraDetail:Winogradskycolumnsareecosystemsinwhichthebyproductsfromonegroupoforganisms
supportthegrowthofanother(e.g.,Desulfovibrioproducesulfide,whichsupportsthegrowthofgreenand
purplesulfurbacteria).Inthisway,microbesshapetheenvironmenttocreateecologicalnichesforother
organisms.Onaglobalscale,cyanobacteriaaretheorganismsresponsiblefortheoxygenationofEarth.Only
afteroxygenaccumulated(throughphotosynthesis)couldlargerandmorecomplexlifeformsevolve.
www.BioInteractive.org
Published2013
Page3of3