If we swab all the door handles then the front door handle might be the dirtiest because many things touch it like leaves or contaminatid air or smoke from forest fires and hands from other people.

Bacteria are micro organisms that can only be seen with a microscope. Bacteria can be found in all environmments, including high touch areas of a household, such as door knobs, keyboards, light switches etc. Bacteria can live for a very long time on dry surfaces. It is picked up on hands and transferred to other objects and people. Some bacteria can cause infections to people but most bacterias don't. Bacteria from our enviroment can be collected and grown in a petri dishes. Bacteria prefer dark and warm enviroment to grow well

Controlled Variables

• swabs
• petri dishes

Manipulated Variable

• Location of the door handles

Responding variables

• the amount of bacteria in the petri dishes

Step 1: Both particapents put on gloves and a mask

Step 2: Each door handle was swabed thoroughly one at a time

Step 3: Rub the swab over the agar surface in the petri dish

Step 4: Place the lid on the petri dish

Step 5: Label the petri dish with the door handle location make sure that there is a un swabbed petri dish labels as control

Step 6: Repeat the remaining door handles

Step 7: Once done labeling the dishes put them in a safe place that is dark and warm

Step 8: each day for 10 days take pictures of the dishes and observe them

 

Jan 5 2024 (Day 1)

Started observing the dishes, nothing grew so for but lid is moist.

 

Jan 6 2024

The Front door Has a very small white dot of bacteria 

And the back door has two small white dots.

Sizes of both are about 1mm. 

 

Jan 7 2024 

Control is growing tiny dots here and there (probably suggesting the air quality.) the bedroom has nothing,

The backdoor has bigger bacteria bubbles with a white-beige colour, the front door is the same, the storage room has spread out bacteria bubbles that are quite small,

The bathroom is surprisingly the same as the front and the back door.

 

Jan 8 2024

The control is the same as yesterday with no noticeable changes, the bedroom is the same as yesterday the backdoor has gotten bigger bacteria bubbles,

The bathroom bacteria bubbles have gotten a tiny bit bigger, the storage rooms bacteria has gotten a bit bigger.

 

Jan 9 2024 (day 5)

• Owens house

Control has many dots of bacteria scattered everywhere on the petri dish.

Bedroom is pretty much the same as Control.

Backdoor bacteria has grown a bit.

Bathroom has grown some black bacteria with some fuzzy looking bacteria and most other bacteria has grown a bit bigger.

Storage room is the same as the control but has slightly larger bacteria bubbles.

Front Door has a blob of bacteria with a more opaque center and other bacteria blobs that are a bit of the same.

• Miles' House:

Control has a couple of tiny cream colored spots.

Bedroom had one black fuzzy culture, 3 cream coloured, and one small yellow culture.

Backdoor had one large and one small black fuzzy culture and one small cream coloured culture.

Bathroom had 2 small cream coloured spots

Storage room had one small dot of cream coloured bacteria

Front Door had two large black fuzzy cultures, one small cream coloured culture.

Jan 14 2024 ( Day 10) 

• Owen's House 

Control had 3 medium sized cream coloured cultures and one translucent spot of bacteria, many tiny cream coloured dots of bacteria scattered throughout the dish.

Bedroom had one medium and many tiny cream coloured bacteria scattered thoughout.

Backdoor had one large, three medium and many tiny dots of cream coloured bacteria throughout the dish. 

Bathroom had one large black fuzzy culture, small amount of translucent bacteria, 5 medium- large cream coloured bacteria, one medium translucent culture, many scattered dots of cream coloured bacteria.

Storage room had a medium black fuzzy culture with translucent border, 3 large cream colored bacteria cultures, one medium sized yellow mustard culture, many scattered cream sized dots

Front Door had 2 medium sized cream coloured bacteria cultures, one large translucent culture, and one large cream coloured glob, many tiny cream coloured dots scattered through out 

• Miles' House

Control had a couple small specs of cream coloured bacteria cultures.

Bedroom had 2 large black fuzzy cultures of bacteria and one medium orange circular culture of bacteria.

Backdoor had 3 large black fuzzy cultures and 3 small cream cultures

Bathroom had 3 small cream coloured bcaterial cultures.

Storage room had 2 small cream coloured cultures and 1 small translucent culture

Front door had 2 large black fuzzy cultures 

Our hypothesis was that we thought the front entrance door handle will be the dirtiest door handle because it's on the outside where many things touch it like leaves and contaminated air from smoke from forest fires.

However, after looking at the bacteria that was on our petri dishes on day 10, it looked like in Miles’ house the back door was the dirtiest, while in Owen’s house the bathroom door handle was the dirtiest based on how much bacteria grew and the size of the cultures.

Based on our analysis we decided that the total number of bacteria cultures will determine the dirtiest door handle.

In conclusion, we found out that for Owen’s house the outside of the bathroom door handle was the dirtiest out of the six door handles we did. 

The outside of the back door at Miles’ house was the dirtiest door handle out of the six door handles we did.

Our results were inconclusive for determining which is the dirtiest door handle. We have disproven our hypothesis meaning we have gotten different results than what the hypothesis stated. We may have gotten more accurate results with a larger sample size (more houses swabbed).

The information gained from this experiment is helpful to know that your door handles always have some bacteria living on them, some more than others. This is a good reminder of the importance of hand washing and to frequently wash high touch surfaces like door handles.

 

• Temperature and humidity of each house could vary 
• Miles' petri dishes collected quite a bit of moisture underneath the lid, making it difficult to see the bacteria 
• small sample size (the number of houses we tested)

Sources for the reserch:

https://kids.britannica.com/

https://www.cdc.gov/

https://www.stevespanglerscience.com/lab/experiments/growing-bacteria/

We would like to thank:

• Owen's parents
• Miles' parents
• Ms. Caddel
• Mr. Pederson