| Explore | Plants are multicellular, eukaryotic organisms that photosynthesize. Through photosynthesizing, they are able to use energy from the sun to grow and reproduce. Just like any other organism, plants can fall sick too. If a virus infects a plant, it kills the plants’ cells as it reproduces, causing the plant to succumb to disease over time due to the viruses populating the plants’ cells rapidly. If a bacterium enters a plant cell, it often secretes toxins that directly affect the host structural/signaling proteins that allow for a proper environment. As the bacterium does this, it injures the host, causing a disease to develop over time. We looked more closely at potatoes, which are widely used in the cooking industry. We wanted to investigate how different pH’s affect the bacteria infecting the potatoes, such as if bacteria in more acidic/basic pH’s cause more rotting or do the opposite and preserve potatoes instead. |
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| Research Question | We want to test how infected potatoes fare under different pH conditions. This information could be important to understand how bacteria can cause disease. We came up with this question because the results could be useful to know what the best conditions are for potatoes to be kept in. |
| Predictions | Our prediction is that the potato at pH 7 will show the most rot. We then predict that, at the lower and higher pH’s, the potatoes will present less rot. We can make these predictions because we previously know that most bacteria work best around neutral pH (7.0). |
| Experimental Design | The 5 potatoes were inoculated with a bacterial solution at four different points using a toothpick inserted 1 cm deep into the potatoes. 5 different solutions with 100 mL of water were created into which we put capsules to change the pH’s. We used pH’s of 12, 10, 7, 4, and 2, with pH 7 as a control. These different pH’s were used so that there would be a significant variety of pH’s used (very acid and very basic) in order to ensure accurate results. We used these solutions to soak the paper towels (40 squirts from a pipette per towel) which we then wrapped around the inoculated potatoes. The potatoes were then each placed into two plastic bags labeled with the pH level. The potatoes were then left in the bags for several days at a constant temperature to allow the bacteria to grow and infect them. We observed the potatoes every few days and scored them based on three scales of 1 to 5, with 5 being the worst and 1 being the best. These scales scored scent, softness, and discoloration. Additional qualitative observations were also made regarding texture and other physiological differences. All observations were recorded in our individual lab journals. |
| Conclusion | The results show that the potato in the pH 7 solution rotted the most based on scent, softness, and discoloration. The basic potatoes had an insignificant difference between them in terms of scoring, and all of them showed less rot in all categories in comparison to the control. The potatoes in acidic solutions had by far the worst scent, but did not smell rotten. Instead they smelled very sour. They also had the least discoloration and only slight softness. Based on the results obtained, we can infer that the bacteria were most effective at the neutral pH. This could be because the bacteria were best suited to a pH neutral environment and thus infected the potato at pH 7 worse than the other potatoes. Some limitations in this lab are that when we wet the paper towels with the different solutions, we tried to keep the droplet sizes the same. However, some of the droplets may have been bigger/smaller than others. As a result, some paper towels may have been more moist than others. There are multiple different future experiments that could be conducted based on these results. For example, different types of potatoes could be tested to see how they react at different pH’s. Some potatoes could be more efficiently stored at different pH’s than other potatoes. In addition, all sorts of different vegetables could be tested at different pH’s to find what is the best way to store them before selling them to the public. These experiments could be useful for the agriculture industry because they could help discover ways to store potatoes and other vegetables for longer periods of time. This could make the shelf-life of these vegetables longer, allowing the agricultural industry to save money that would otherwise be lost due to rotten vegetables. |