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Name:ChelseaYe

DiscoveringtheConditionsThatPromotetheGrowthof

Bacteria

I) Problem:Whatkindofmicrohabitatsmosteffectivelypromotesthegrowthofbacteria?

II) BackgroundInformation:Eventhoughwecantseethem,microbesarepresentwherevertheproper

conditionsexisttosustainlife.Theyliveinandonhumansandother

animals,aswellasonplants.Theyalsoliveinthewater,soil,andair.Inthisinvestigation,youwillscavengeforbacteriainvarious

microhabitats.

Bacteriaaresimpleandsmall;theyaresingle-celledprokaryotes,typicallyonly1micrometerindiameter.Theyareamongthemostnumerouslifeforms

ontheplanet.Bacteriacanbefoundeverywhereotherlifeexistsandevenmanyplacestooextremeforlargerorganisms.

Bacteriaaresosmallthattheycannotbeseenwithouttheaidofa

microscope,sopeopledidntknowtheyexistedatallbefore1676whenAnton

vanLeeuwenhoekusedhishandcraftedmicroscopesandkeeneyetoobservethebacterialivinginadropletofwater,

Bacteriacanbecultured,orgrown,onnutrientagar.Nutrientagarisa

jellylikesubstanceextractedfromseaweedtowhichnutrientshavebeenaddedsothatbacteriaorothermicroorganismscabbegrownonit.If

conditionsarefavorable,bacteriawillrapidlyreproducebydividingintwo.Eventually,bacterialreproductionproducesspotsonthenutrient

agar,eachofwhichconsistsofthemanydescendantsofasinglebacterium.Thesespots,whicharevisibletotheunaidedeye,arecalledcolonies.

Bacteriagrowbestinwarmareas,alsoinbodytemperature.

III) Hypothesis:

Ifbacteriagrowbestinwarmplacesthenasampleswabbedfromamicrowave/heatingventwillproducealargenumberofbacteriacolonieswhen

swabbedonadishofnutrientagar.

IV) ExperimentPlan:

Materials Nutrientagarplates

Chinamarker Applicatorswabs

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Procedure

1) Besuretofollowsteriletechniquesduringthislabsothatcontaminationdoesntoccurandruintheresultsofthislab.

2) Usingthechinamarker,drawalineonthebottomofyournutrientagarPetridishdividingitinhalf.Numbereachhalfwithadifferentnumber.

3) Selectavarietyofmicrohabitatstotestforthepresenceofbacteria.Recordthemicrohabitatsinyourdatatable.Identifycharacteristicsof

thismicrohabitatandrecordinyourdatatable.(wetordry,lightordark,cleanordirty,isolatedorhigh-traffic)

4) Withasterileapplicatorstick,swabthegivenmicrohabitat.5) Streaktheswabacrossthecenterofthenutrientagarplatesectionina

straightline,beginningandendingabout2cmfromeachedgeofthedish.

Donotbreakthroughthenutrientagar.Trytokeepeachstreakmarkthesamesize.Remember,youwillbeapplyingtwodifferentstreakmarksfrom

twodifferentmicrohabitatstoeachnutrientagarplate.Keepthecoveroffthedishforaslittletimeaspossible.

6) DiscardtheapplicatorstickinthemannerinstructedbyMr.Ogden.7) Repeatsteps4-6fortheothermicrohabitats.8) Mr.Ogdenwillleaveonedishuntouchedasacontrol.9) Incubatethedishesforatleastfivedays.10) Recordthegrowthofthemicroorganismoneachplateinbothqualitative

andquantitativetermsinthedatacollectionsectionofthislab.

ExperimentalComponents

Manipulated(Independent)VariableTheareainwhichthebacteriaaretakenfromisthemanipulatedvariable.Responding(Dependent)Variable:Theamountofbacteriainasectionistherespondingvariable.Controlled(Constants)Variables:Samekindoffood(agar)KeptinsametemperatureSametypeofcontainer

Control:adishwithoutanybacteriaputintoit

V) DataCollection:

Observations:

Section1:2(white,smuggledcoloring)bigcolonies,5bigclearcolonies,someyellowandorangedots

Section2:1hugecolonyofbacteria(looksthin,whiteanddarkinthecenter),lotsofsmallerones.

Section3:Notalotofbacteria,fewdots

Section4:1hugecolony(whiteyellow,smuggled).Therearemanysmallerwhiteandyellowcolonies.

Section5:1white,fuzzycolonyhugesize,andmanyyellow/orangecoloniesmediansized.

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Section6:1bigcolony(tan,smudged),manysmallercolony(yellow,

white) Section7:(control)nobacteria,lightyellow

DataTable:

Section

NumberMicrohabitat Microhabitatcharacteristics:

dry/wet,clean/dirty,light/dark,

isolated/high-traffic

Amountofbacteria

10-numerous/1-veryfew1 Microwave Hot, 82 Hotlaptop Warm,Dusty 83 Fridge/Freezer Cold,Clean,Dark 14 Hand BodyTemperature,High-traffic 55 TechLab Cold,Dusty 76 HeatingVent Dusty,warm 67 Control

(untouched) --------------------------------------------------- 0

Photographs:

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Conclusion

1)Whywasitimportanttokeeptheagarplatesuncoveredforaslittletimeaspossible?

Itisimportanttokeepagarplatesuncoveredforaslittletimeaspossible

becauseunpredictedbacteriamightfallintotheplate.Forexamplethedustfortheceilingofbacteriaintheairmightfloatin,soitcoulddisruptthe

otherbacteriagrowth.

2)Whywasitimportanttoobservesterilemethodsanduseanew,sterileswab

foreachdifferentmicrohabitat?Ifyouusethesameswabeverytimethenthebacteriafromothersubstances

couldruboffintothewrongsection.Thiscouldmakeallofthesectionsthesame.Youalsohavetoobservesterilemethodsbecauseifyouswabonesection

twice,orifyoubroketheagarthenyouwillhavemorevariablesthenyou

accountedfor.

3)Whywasthenutrientagarsterilized(madefreefrombacteria)beforetheinvestigation?

Thenutrientagarwassterilizedbecauseifithadextrabacteriainsomeplacesthenyouwouldhaveinaccuratedata.Foriftherewasalreadybacteria

inonesection,youwouldgetitconfusedwiththetruebacteria.

4)Earlybiologistsgrewbacteriaonfreshlycutslicesofvegetables.Whywoulditbeimportanttohavefreshlycutvegetableslices?

Itisimportanttogrowbacteriaonfreshlycutvegetablesbecausevegetable

developmoldoveralongperiodoftime.Soitwouldlooklikebacteriawhenitisactuallymold.

5)Whatwasthepurposeofthecontrol?

Thepurposeofthecontrolwastocompareitwithyourbacteriagrowndishes.Youcanobservethegrowthofbacteriabetterwhenyouhavethecleandishto

compareitto.

6)Whichmicrohabitatseemedtoresultinthemostbacterialgrowth?Accordingtomyobservationswarmerhabitatsresultinthemostbacteria

growth.Sections1,2,4,and6seemtohavenumerousamountsofcolonies.1,2,4

and6areallthewarmerplaces.

7)Asidefromthecontrol,whichmicrohabitatseemedtoresultintheleastbacterialgrowth?

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Asidefromthecontrol,coldmicrohabitatsseemtoresultintheleast

bacterialgrowthaccordingtomyobservations.Section3haslittletonobacteriagrowthbecauseIgotthissamplefromafreezer/fridge.5isalsoina

coolplacebutitisaveryhigh-trafficarea.

8)Whatkindsofmicrohabitatcharacteristicsseemtohavethegreatestimpactonthegrowthofbacteria?

Warmandhigh-trafficareasseemtohavethegreatestimpactonthegrowthofbacteria.Forexamplesection3grewnobacteriabecauseitwastakenfroma

coldplaceandasemi-lowtrafficarea.

9)Therearethousandsofdifferentkindsofbacteria.Doyouthinkthatshape

aloneisenoughtoidentifyaparticularspeciesofbacteria?Why?Ithinktheshapealonecannotidentifyaparticularspeciesofbacteria.I

knowthisbecauseinmybacteriasectionsthereweresomebacteriacoloniesthathadthesameshapebutdifferentcolors.Thosetwocoloniesofsameshape

butdifferentcolorweremostlikelydifferentspeciesofbacteria.

10)Doallthebacteriacolonieshavethesameappearance(i.e.color,shape,andsize)?Ifnot,whatdoesthatindicate?

Thebacteriacoloniesdonotallhavethesameappearancebecausetherecouldbedifferentkindsofbacterialivinginthesamearea.Forexampleinsection

4therearedifferentcoloredcolonies,thisisbecauseonmyhandtherecould

havebeendifferentspeciesofbacteriafromtheplacesItouched.

Reflection

ColleenandItestedthesamehypothesis(Ifbacteriagrowbestinwarmplacesthenasampleswabbedfromamicrowave/heatingventwillproducea

largenumberofbacteriacolonieswhenswabbedonadishofnutrientagar.)butwegottotallydifferentresults.Colleenssampleofthe

fridge/freezerhastonsofbacteriacolonieswhileIhavealmostnobacteria

growingthere.Thismaybebecauseweswabbeddifferentplacesinthefridge/freezer.Therecouldhavebeenaspillthere,butIstillthinkit

shouldhavebeenthesame.Thisunpredictedbacteriagrowthhasbeenveryintresting.

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ColleensSection3

(freezer)

MySection3(freezer)

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