Transcript Bacteria: The Lasting Fingerprint?

Jenny Zack
Grade 9
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The problem addressed in this experiment
was whether or not bacteria can be used to
identify suspects in a crime scene.
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Microbiome
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182 species
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Staphylococcus, Corynebacteria,
Streptococcus, Escherichia coli, Myobacteria,
and Haemophilus
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If the bacteria are treated with antibacterial
cleaner and mouthwash, then they will be
ineffective as identifiers.
If the bacteria are left out for three days, then
they will multiply, and can be used as
identifiers.
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12 Petri dishes
Tryptic soy agar
Easy Gel coliscan
18 sterile cotton swabs
3 Inoculating loops
Antibacterial cleaner
Mouthwash
Paper towels
Sterile surface
Incubator
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First, I made a tape square on the
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surface of a table. I then made multiple
bacterial handprints within that square
to let it sit for the weekend and see
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how time affects it.
Next, I made a bacterial handprint on a
table’s surface and sprayed the table 
with antibacterial cleaner. I then wiped
it with a paper towel and took three 
samples.
For the mouthwash group, this routine
was repeated, but I wiped the bacterial
handprint with mouthwash.
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When making the control samples, I
made a bacterial handprint and took
three samples without treating it with
anything.
For time, the same process was
repeated, however the bacteria was
allowed 3 days to sit prior to testing.
Lastly, I placed all nine petri dishes
in the incubator at 26 degrees
Celsius.
All petri dishes were taken out of the
incubator after 3 days of growth.
When examining the samples, I
counted the # of colonies and colony
types. I distinguished colony types by
color.
After I examined the petri dishes, I
put them in the fridge to preserve
them.
700
600
Amount of Colonies
500
400
300
200
100
0
Control
-100
Anti
Mouth
Conditions
Time
80
70
Number of Colonies
60
50
40
Control
Time
30
Anti
20
Mouth
10
0
-10
-20
Yellow
White
Beige
Orange
Bacterial Types
Green
Black
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The hypothesis was partially supported
because despite the use of the antibacterial
products and mouthwash, bacterial growth
was comparable to the control samples.
Also, bacterial growth was greater in the time
samples than the control.
Given the results it is inconclusive whether or
not these bacterial handprints can be used to
identify suspects
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“Growing Bacteria.” Science Enterprises. N.p., n.d. Web. 29 Sept. 2011.
<http://www.scienceenterprises.com/growingbacteria.aspx>.
HomeScience. “How to Grow Bacteria.” Youtube. N.p., 15 Feb. 2010. Web. 29 Sept. 2011.
<http://www.youtube.com/watch?v=1VkB8NzrEBs>.
“Human Skin Has Many More Types of Bacteria than Previously Thought.” Medical News
Today. MedPage Today Professional, 2007. Web. 25 Jan. 2012.
<http://www.medicalnewstoday.com/releases/62423.php>.
Madrigal, Alexis. “Your Leaving a Bacterial Fingerprint on Your Keyboard.” Wired. Conde
Nast Digital, 2010. Web. 29 Sept. 2011.
<http://www.wired.com/wiredscience/2010/03/keyboard-microbiome/>.
Martinez, Edecio. “Your Germs Might Be as Unique as Your Fingerprints.” CBSNews. CBS
Interactive Inc., 2011. Web. 29 Sept. 2011. <http://www.cbsnews.com/8301504083_162-20000536-504083.html>.
“Telltale Bacteria.” The Engineer. Centaur Media plc, 2011. Web. 26 Sept. 2011.
<http://www.theengineer.co.uk/news/telltale-bacteria/1001384.article>.
Thank you to everyone in the audience for listening to my
presentation! I would be happy to answer any questions you
may have about my project!