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Bacteria Growth in the Mouths of Humans and Canines

A Scientific Inquiry project exploring whose mouth is cleaner: a human's or a dog's?

Melissa Ayers

on 30 October 2012

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Transcript of Bacteria Growth in the Mouths of Humans and Canines

Bacteria Growth in the Mouths of Humans and Dogs Question Through observation data and photographic comparisons, the results show that a human's mouth is cleaner than a dog. The hypothesis was correct! Conclusion Is a dog’s mouth cleaner than a human’s mouth?

I will test this by measuring the amount of bacteria growth in humans and in dogs. Hypothesis Bacteria growth will show that a dog's mouth is not cleaner than a human's. Materials 3 dogs (small, medium, large)
3 humans (child, male adult, female adult)
6 large, 10 cm (4 in) diameter Petri dishes
6 cotton swabs
5 grams of Nutrient Agar
1 600 mL plastic beaker
1 cup f hot water
Digital SLR camera for recording Variables Independent – Species (human or dog)
Dependent – Amount of bacteria
Controlled – time samples were taken, location of mouth where samples were taken (the cheek) Mix 5 grams of agar with 1 cup of hot water and stir
Bring this mixture to a boil for one minute to completely dissolve the agar
Allow mixture to cool for 3 to 5 minutes
Fill the bottom half of the Petri dish 1/2 full with the warm nutrient agar solution
Cover each Petri dish with the lid
Allow the solution to cool and harden for at least an hour
Immediately move to next step to avoid unwanted contamination Procedure Procedure continued Label each Petri dish to identify which sample came from where
Use Digital SLR camera to record results every 3 days
Make observations of growth, changes in color, and any patterns in bacteria
Record results and safely dispose of closed Petri dishes in zip lock bag Procedure continued Within the same day locate and swab the cheek of 3 humans and 3 dogs
Thoroughly swipe the cotton swap on the cheek of the subject
Immediately lift the lid of Petri dish and lightly draw a squiggly line in the agar with the end of the cotton swab
Cover the Petri dish with lid and place the dish in a safe, dark place to let the bacteria grow Data was collected every 3 days over the course of 12 days
Data was recorded through photographs with digital SLR camera
Observations were recorded each time pictures were taken noting the size, color, shape, and growth of bacteria Data What will the Agar do? Day 1
All Agar and Petri Dishes look the same for all subjects Subjects 31 year old adult male Matt 23 year old female adult Melissa 7 year old male child Bradley A 10 year old English Mastiff that spend the majority of her time indoors. Maggie 5 year old Dachshund that spends the majority of her time outside in the yard. Bella 10 month old Welsh Corgi puppy, mostly indoors but outsides sometimes. Bailey Day 6 Visual Data by subject and day I have organized the samples by subject and in the order they were documented (every 3 days). This is a visual representations of the observations I noticed when checking on the bacteria. Every 3 days I checked in and took a photograph to document the changes in size, shape, and color that I saw personally. These can all be seen in the following slides. Matt Day 12 Matt Day 9 Matt Day 6 Matt Day 3 Melissa Day 12 Melissa Day 9 Melissa Day 6 Melissa Day 3 Bradley Day 12 Bradley Day 9 Bradley Day 6 Bradley Day 3 Maggie Day 12 Maggie Day 9 Maggie Day 6 Maggie Day 3 Bella Day 12 Bella Day 9 Bella Day 6 Bella Day 3 Bailey DAY 12 Bailey5 Day 9 Bailey Day 3 Matt Day 12 Melissa Day 12 Bradley Day 12 Bella Day 12 Bailey DAY 12 Final Comparisons Day 12 Who was dirtier? Maggie Day 12
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