For our experiment, we selected five commonly touched  surfaces to test bacterial growth: the door handle, bathroom surfaces, teacher's computer, water fountain, and desk. Our hypothesis is that these surfaces may contain a lot of bacteria and the water fountain would be the dirtiest. Each of us made a list of the surfaces. The ranking scale ranged from 1 (indicating the cleanest) to 5 (representing the dirtiest). This way we can compare our prediction to the actual result and see how clean these everyday items really are.

Yasmine                              Layla

1.desk                               1.desk

2. Computer                      2.door handle

3.bathroom                       3. computer 

4.door handle                   4.bathroom

5. Water fountain.             5.water fountain

There are four stages of bacterial growth/development : lag, logarithmic (exponential), stationary, and death. The period in the life of the bacterial population when cells are adjusting to a new environment before they start to increase in growth is called the lag phase.The logarithmic phase is when cells divide and start to increase exponentially.Stationary phase is when cells remain metabolically active but the growth ceases (come to an end).lastly death,  when living cells stop functioning metabolically and start the process of death. 

So we can make sure this experiment works we need to know the conditions/factors that are necessary for bacterial growth.The temperatures, moisture, oxygen levels, pH levels and nutrients.  Between 5 to 57 °C is known as THE DANGER ZONE Most bacteria that cause disease grow fastest in this temperature range. Some bacteria thrive in extreme heat or cold, while others can survive under highly acidic or extremely salty conditions.Bacteria grows the best Close to 7.0. natural pH. pH influences the microorganisms occurrence and distribution.Different types of bacteria require different types of moisture but the majority require relative humidity (RH) of 60% or more.Bacteria require a minimum oxygen level that has to be just right about 1% to 10% below the 21% in the atmosphere but while there are some bacteria species grow anaerobically (when there is no oxygen in the atmosphere). For all bacterial species to grow they require a medium that contains a suitable source of food (nutrients).

Bacteria can be beneficial or harmful to humans. Many bacterial species are pathogenic, when they infect humans they cause diseases and maybe death. For example: Staphylococcus aureus, Streptococcus pyogenes, Pseudomonas aeruginosa, Escherichia coli. However, other commensal (none harmful) bacteria strains, for example: Bifidobacterium and Lactobacillus help us by digesting cellulose (fibers from vegetables) which we can’t digest ourselves. These bacteria also produce chemicals that help protect our gut and skin from other pathogens.

There are too many ways to identify bacterial species, some of these ways are morphological (the shape of bacterial colonies), biochemical testing (serieses of biochemical reactions) and molecular (looking for gene sequence that is specific for a particular bacterial strain). 

We want to find the best cleaning supplies for these school surfaces (If they turn out dirty). Any cleaning sprays that contain Bleach solutions is a good option  because the active ingredient in bleach  (Hypochlorite acid) Causes there to be less protein. Although citric acid may not be the best choice  it has an effect on killing bacteria And is perfect if you don't have any cleaning supplies at the time because it is found in Limes and lemons and other citrus fruits which  can be found in almost every household. Hydrogen peroxide is a very common ingredient to be found in cleaning sprays Because it's very strong. A very popular Cleaning Supply that uses hydrogen peroxide is Lysol. 

Lysol

Controlled: Temperature, time for growth, Amount of nutrients, humidity. 

Independent/manipulated: Changing gloves each time So bacteria don't get mixed, Different tubes for each surface, surfaces, cotton swabs So bacteria don't get mixed,

Dependent/Responding: which surface is the dirtiest, and which has the highest number of bacteria on it?

1. We prepared tubes with 250 microliters of saline solution in each tube with adalt supervision.
2. We selected 5 different surfaces to swab( desk,table, door handle, computer, bathroom, water fountain).
3. We wore gloves and dipped the swab in the saline solution to wet it then we swabbed each surface and put the cotton tip of the swab inside the tube and closed it. We repeated this step 3 times for each surface.
4. In the lab we diluted the samples ten times and spread the solution that contains the collected bacteria on the agar plates with adalt supervision.
5. We incubated agar plates in the 37°C incubator for 24 hours.
6. We counted the number of bacterial colonies in each plate then we calculated the average number of colonies for each surface.
7. We made a histogram of the results.

After 24 hours in the 37-degree incubator, we noticed that the least expected surfaces were the dirtiest the desk was the dirtiest followed by the doorknob then the water fountain then the bathroom, and the cleanest was our teacher's computer. This list surprised us because we thought that the water fountain would be the dirtiest. After all, it is touched by many people. We also observed that some of the bacterial colonies grew really close the eachother and some were very far from each other.we noticed that many people thought that the bathroom and water fountain were going to be the dirtiest.

the bacteria in the bathroom and water fountain will probably be cleaner than the desks and doorknobs because the bathroom usually gets cleaned by staff at the end of the day and people probably wouldn't think to clean doorknobs. Desks don't get cleaned very often or as nicely as bathrooms and water fountains in our school. Some bacterial colonies grew closer to each other than others because it was random they were all swabbed and the places the bacteria were left were different for all agar plates. 

After we tested all the five commonly touched surfaces for bacterial growth  we were surprised by the results. Previously we thought that all these Services may contain a lot of bacteria but the dirtiest would be the water fountain and in our hypothesis we also made a list of what we thought was the cleanest to the dirtiest 1 (indicating the cleanest) to 5 (representing the dirtiest). After we got the results we compared both of our  lists  and we were very wrong. We both thought that desk was going to be the cleanest and it ended up the dirtiest. In conclusion the  cleanest was the computer and the dirtiest was the desk.

Yasmine                Result                    Layla 

1.desk                  1.computer            1.desk 

2. Computer         2.Bathroom           2.door handle 

3.bathroom           3. Water fountain 3 . computer 

4.door handle       4. Door Handle     4.bathroom 

5. Water fountain. 5.desk                   5.water fountain

People would be interested in knowing our results because they could see how dirty everyday touched surfaces are and how they could make it cleaner. They may also feel safer in public bathrooms and water fountains because they came out cleaner than we thought and that is probably because they clean those areas regularly. They may also be interested in knowing that door noobs and desks/tables are very dirty so they can apply more precautions, such as washing their hands after touching these surfaces.

We could do our experiment better and more beneficial next time by swabbing more places that we haven’t considered in our current research like lockers,gym equipment, and stair railings.

during this experiment, there could have been many times when things could have gone wrong but luckily we had Yasmine's dad to show us how to swab for when we did it on the school surfaces and to supervise us when we swabbed on the agar plates.so we were very careful when we performed our experiment. but here are the errors we could have made: we could have swamped wrong, forgot to put on the saline solution or used the wrong solution, we could have forgotten to change our gloves which would mean the bacteria could have gotten mixed, we could have swabbed on the agar plate or did the dilution wrong, could have accidentally put one of the agar plates in the incubator for longer and when we counted the bacterial colonies that had grown on the agar plates could have counted the amounts wrong and still might have but we tried our best so the results are probably almost accurate.

https://www.thoughtco.com/bacterial-growth-curve-phases-4172692

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3264077/#:~:text=Lag%20time%20is%20defined%20as,environment%20before%20starting%20exponential%20growth.

https://www.scientificbio.com/blog/what-are-the-stages-of-the-bacterial-growth-curve/#:~:text=Log%20(Exponential%20Growth)%20Phase&text=This%20is%20when%20cells%20divide,necessary%20steps%20required%20for%20reproduction.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5650638/#:~:text=Stationary%20phase%20is%20the%20stage,confer%20viability%20to%20the%20bacteria.

https://www.scientificbio.com/blog/what-are-the-stages-of-the-bacterial-growth-curve/#:~:text=As%20waste%20builds%20up%20and,time%20and%20exponential%20decay%20begins.

https://www.aatbio.com/resources/faq-frequently-asked-questions/what-are-the-factors-that-affect-bacterial-growth

lysol.com/products/multi-purpose-cleaners/lysol-with-hydrogen-peroxide-multi-purpose-cleaner#:~:text=Lysol®%20with%20Hydrogen%20Peroxide,clean%20with%200%25%20bleach∞!&text=Lysol®%20with%20Hydrogen%20Peroxide%20Multi-Purpose%20Cleaner%20can%20be,Walls

https://www.cdc.gov/hygiene/cleaning/cleaning-your-home.html#:~:text=Bleach%20solutions%20will%20be%20effective,disinfecting%20surfaces%20using%20bleach%20solutions.

https://pubmed.ncbi.nlm.nih.gov/32273009/#:~:text=A%20citric%20acid%20concentration%20of,hypochlorite%20was%20effective%20against%20M.

we acknowledge mrs. pond because she helped organize the whole grade 7s and some grade 8s she also helped us know the steps in making are project and ran the science fair we would also like to acknowledge Yasmine's dad for taking us to the lab to test are experiment and supervising us we also acknowledge the judges for taking time out of there day to judge us