4.1 Key Findings, Comparison and explanations

4.1.1 Key Findings

From the data collected, we can see that the bread that spent the longest time in contact with the floor had the fastest and most growth of bacteria after 3 days while the bread which was in contact with the floor for 5 seconds had the slowest and least growth of bacteria. There was no growth in bacteria for the control set up (no bread at all) and the bread which was in contact with the floor for 0 seconds. The set up with the highest growth of bacteria was the one with bread dropped on the floor for 300 seconds, with 9.7 increase in the number of colonies of bacteria, from 15.3 on Day 1 to 25 on Day 3. The lowest growth of bacteria was that of the bread, which was dropped on the floor for 5 seconds, with a 0.7 number increase from Day 1 to Day 3, 10 colonies of bacteria to 10.7 colonies of bacteria.

In our first experiment, the bread which was dropped for 30 seconds had more colonies of bacteria than that of the bread that dropped for 60 seconds. The difference was vastly different, with the average for Day 1 for the 30 seconds being 11 colonies of bacteria while the average number of colonies of bacteria for the 60 seconds was 0.67. Thus we redid our experiment, hoping to get more accurate results.

4.1.2 Comparison with other research

In a similar experiment done by Brookshire (2017), she dropped bologna on the floor to test her hypothesis that food picked up off the floor after five seconds will collect fewer bacteria than food left on the floor for 50 seconds. She had 6 experiments in total; one was a control, one grew microbes from bologna that had never been dropped. The other four hosted bacteria swabbed from bologna that sat for five or 50 seconds each on sections of the clean and dirty floor.

Her results show that the “never dropped”, “5 second on clean floor”, and “5 seconds on dirty floor” experiments had similar results after 3 Days, with about an increase in 50 colonies grown since Day 1. The “50 seconds on clean floor” and “50 seconds on dirty floor”, however, had only increased to around 30 colonies grown since Day 1. The control also grew to about 9 colonies after 3 Days.

Comparing her “never dropped” experiment and the experiments done on the dirty floor to our experiments, her results show that as the number of seconds increases (50 seconds), the number of colonies grown decreases. She concluded that microbes show up, whether or not food has touched the floor, and time doesn’t matter when it comes to keeping the food clean Brookshire (2017). This contradicts our experiment, which shows that as time in contact with the floor increases, the growth of bacteria increases as well. When food has not touched the floor (0 seconds), there would be no bacteria growing on it.

4.1.3 Explanations of key findings

There was faster growth of bacteria on the bread which was in contact with the floor for a longer time. This suggests that the bread, when in contact with the floor for a longer period of time, collected more bacteria and thus, the larger amount of bacteria multiplied more and faster, resulting in faster and more growth of bacteria. As the bread in contact with the floor for 5 seconds also had bacteria growth, we can conclude that food or any items can pick up bacteria the moment it touched the floor or any surfaces with bacteria. So regardless of the amount of time spent in contact with the floor, as long as it was in contact with the floor, the food will still pick up bacteria. Although the longer the time spent in contact with the floor, the more bacteria will be collected.

4.2 Limitations and Recommendations

The methods and procedures used to carry out the experiment have been revised and checked to ensure that there are lesser shortcomings in the experiment. Nevertheless, there are still limitations to our experiment due to factors such as the lack of equipment or human error.

One such limitation is the method of measuring bacteria. At first, we wanted to use software to count the number of colonies in the agar plates. However, we were unable to find the software and thus ditched the plan and used a simpler method.

In order to improve on this limitation, we could have used software or by using a colony counter. Furthermore, if we still had to count the grids of bacteria, we could have drawn smaller grids with a size of 0.50 cm x 0.50 cm, for a more accurate count of the number of bacteria. Both improvements would have increased the precision and accuracy of the results.

Another limitation is the distribution of dirt onto the surface. We are unable to evenly distribute the amount of bacteria and dirt across the surface as there would be uneven surfaces on the table. As a result, some parts of the table may have more dirt and bacteria than other parts, and the result may be affected by it.

To solve this we could use machinery to swab the pieces of bread and to spread the dirt. This would allow the accuracy of the experiment to be higher and more equal. One other improvement would be to use the same amount of pressure to press onto the bread when the bread is on the dirt solution.

Last but not least, when collecting the data over the span of 3 days, we counted the colonies at different times each day which was also a different timing from the time we first put the agar plates into the incubator. Thus, on Day 1 till Day 3 the bacteria on the agar plates would have had less than or more than 24 hours to cultivate, affecting the reliability of our results.

In order to solve this problem, we could have taken note of the timings we placed the agar plates with bacteria into the incubator on the day of the experiment and made sure to count the number of bacteria on the agar plates on Day 1 till Day 3, at the same timing so that the bacteria on the agar plates would have been given exactly 24 hours to cultivate each day, making the results more accurate.