Transcript Petri Dish investigation

Petri Dish
investigation
agar
A gelatinous material
derived from certain
marine algae.
used as food for
bacteria and as a
thickener in many
food products
(carrageenan)
inoculate
To introduce microorganisms or infectious
material into a culture
medium.
The “Clamshell” method
Turn the dish upside down when streaking
to avoid germs from the air landing on the
dish.
streak
To make lines
method of inoculating
to make sure “germs”
get all over the plate
Sterile
Free from live bacteria or other
micro-organisms:
a sterile
operating area
sterile instruments.
autoclave
Shape of bacterial cells
a) Cocci - round
bacterial cells.
(cox-eye).
A
B
b) Bacilli - rodshaped bacterial
cells.
c) Spirilli
(corkscrew) spiral-shaped bacterial
cells
C
QHEIC-the Scientific Method
Question
Hypothesis
Experiment
Interpret data
Conclusion
Variables
Independent Variables
The factor that is
purposely changed
EX: The different
locations to be
swabbed
Dependent Variable
The factor that you
expect to change as a
result of what you
purposely changed.
EX: the amount of
bacteria that grows
Procedure
1) Record the numbers of your dishes on your data
chart and make sure the dishes are divided into A,B, C
and D. Each group will get 1 dish.
2) Go to your first location and use your swab to gently
rub the location. Rub the location for 10 seconds.
3) Invert dish ,open quickly and streak the plate with the
swab.
4) Repeat for other locations after discarding swab.
5) Remember to write down the location on your sheet.
The constants and the control
Constants
The factors that are
kept the same in all
trials
1. Swabbing method
2. Swabbing time
3. Temperature of
room
Control
the trial that is not
exposed to the
varying condition
EX: section D