Petri Dish Petri Dish investigationinvestigation

agaragar

A gelatinous material A gelatinous material derived from certain derived from certain marine algae. marine algae.

used as food for used as food for bacteria and as a bacteria and as a thickener in many thickener in many food products food products (carrageenan)(carrageenan)

inoculateinoculate

To introduce micro-To introduce micro-organisms or infectious organisms or infectious material into a culture material into a culture medium. medium.

The “Clamshell” methodThe “Clamshell” method

Turn the dish upside down when streaking Turn the dish upside down when streaking to avoid germs from the air landing on the to avoid germs from the air landing on the dish.dish.

streakstreak

To make linesTo make lines

method of inoculating method of inoculating to make sure “germs” to make sure “germs” get all over the plateget all over the plate

SterileSterile

Free from live bacteria or other Free from live bacteria or other

micro-organisms: micro-organisms:

a sterile a sterile

operating areaoperating area

sterile instruments.sterile instruments.

autoclave

Shape of bacterial cellsShape of bacterial cells

a)a) CocciCocci - round - round bacterial cells. bacterial cells.

(cox-eye)(cox-eye). .

b) Bacillib) Bacilli - rod-- rod-shaped bacterial shaped bacterial cells. cells.

c) Spirilli c) Spirilli (corkscrew)(corkscrew) - - spiral-shaped bacterial spiral-shaped bacterial cells cells

AB

C

QHEIC-the Scientific MethodQHEIC-the Scientific Method

QuestionQuestion

HypothesisHypothesis

ExperimentExperiment

Interpret dataInterpret data

ConclusionConclusion

VariablesVariables

Independent VariablesIndependent Variables

The factor that is The factor that is purposely changedpurposely changed

EX: The different EX: The different locations to be locations to be swabbedswabbed

Dependent VariableDependent Variable

The factor that you The factor that you expect to change as a expect to change as a result of what you result of what you purposely changed.purposely changed.

EX: the amount of EX: the amount of bacteria that growsbacteria that grows

ProcedureProcedure1) Record the numbers of your dishes on your data 1) Record the numbers of your dishes on your data chart and make sure the dishes are divided into A,B, C chart and make sure the dishes are divided into A,B, C and D. Each group will get 1 dish. and D. Each group will get 1 dish. 2) Go to your first location and use your swab to gently 2) Go to your first location and use your swab to gently rub the location. Rub the location for 10 seconds.rub the location. Rub the location for 10 seconds.3) Invert dish ,open quickly and streak the plate with the 3) Invert dish ,open quickly and streak the plate with the swab.swab.4) Repeat for other locations after discarding swab.4) Repeat for other locations after discarding swab.5) Remember to write down the location on your sheet.5) Remember to write down the location on your sheet.

The constants and the controlThe constants and the control

ConstantsConstants

The factors that are The factors that are kept the same in all kept the same in all trialstrials

1.1. Swabbing methodSwabbing method

2.2. Swabbing timeSwabbing time

3.3. Temperature of Temperature of roomroom

ControlControl

the trial that is not the trial that is not exposed to the exposed to the varying conditionvarying condition

EX: section DEX: section D