Couch Potato <3

Project by group camsdavispgstfall2020

Explore Some things we know about potatoes are that they are root vegetables. Soft rot in potatoes have been caused by a range of bacteria around the world. It survives in soil, decaying plant debris, and in seed tubers. The infection occurs in skin damage on potatoes due to growth cracks or high soil temperatures. Blackleg, a bacterial disease, can cause losses in potato patches. Serious rotting of tubers can occur in storage or in potato hills. Pathogens can come in different forms such as fungi, bacteria, or viruses. They can spread through humans or contaminations and can cause disease symptoms. Sources:,belonged%20to%20the%20genus%20Erwinia. Observations: On Oct.8, after inoculation, Potato #2 had no noticeable changes in smell or color. The texture of the potato wasn't really squishy. On Oct. 13 around 7:15 PM, Potato #2 had a bad odor, there were more brown spots on the paper towel, and the inside of the potato wasn't affected, but still had a mushy texture. For observations on the potato today (the last day), the potato smelled like bad tap water and the places that were poked with the toothpick that had the inoculum were brown. But the rest of the potato seemed pretty normal. There was one part (that was poked with the inoculum) that was mushy.
Research Question Research Question: -Would a different type of water affect the growth of bacteria on the potato?
Predictions One of our predictions is that the saline water (salt water) will keep those potatoes the least affected by bacteria because salt water generally heals wounds and helps skin close, so it might work the same way with potatoes. In addition, salt absorbs moisture, which could help prevent the growth of bacteria because the bacteria typically needs to be damp to grow. Another prediction we have is the sugar-water-covered potatoes will grow the most bacteria because sugar tends to be something that promotes the growth of bacteria (ex. yeast). And as for the tap-water-covered potatoes, we believe that there isn’t anything in the water that could promote or minimize the growth of bacteria because tap water is filtered pretty well.
Experimental Design Our plan to inoculate 10 potatoes with bacteria from potato rot of a different potato and test how the type of water that covers the surface of each of the potatoes (via paper towel) affects the growth of the bacteria. The independent variable is the type of water used to soak the paper towels - tap water, saline water, and sugar water (saturation TBD). The dependent variable is the growth of bacteria on the potatoes - soft spots and dark spots (both measured by size and quantity), and smell (reference Smell-O-Meter). The control is a potato that is wrapped in a dry paper towel. To collect the bacteria, cut one potato in half and place it in a ziploc bag with 50 milliliters of tap water for 3 to 4 days so that the water becomes potato-rot-water (we recommend also placing the bag in a smell-proof container). After the bacteria (inoculum) has been collected, begin to inoculate the rest of the potatoes. There should be 3 potatoes for each water variation, and one for the control as well. Wash the potatoes with tap water (as one normally would) and dip the toothpick in the inoculum and inoculate the potatoes with the bacteria using a toothpick to poke 4 holes in each of the potatoes (one on each end and each side). Make sure to dip the toothpick every time you poke another hole in the same potato. When poking another potato, use a different toothpick (to avoid any possible contamination). Wrap each potato in a paper towel that is damp with its respective water selection and place each in a ziploc bag. Collect data (dependent variable) every day. On the final day, cut open the potatoes to observe if the dark spots look different on the inside.
Conclusion The sugar water made the bacteria of its three potatoes flourish the most compared to the bacteria growth of the other two water types tested. According to the observations, one of the sugar water potatoes had the strongest smell. The same one also had the darkest discoloured water around it and was very mushy. This evidence is also presented on the graph that’s titled, “The Effects of Different Types of Water on the Bacteria Growth on Potatoes”. The bacteria in the sugar water potatoes developed faster because they reached an 11 by day 6, so they were the fastest potatoes to reach an 11 on the smell scale. On day two, they made the largest jump from 1 to 4 on the smell scale while the saline water potatoes only went from a 1 to a 3 and the tap water potatoes only went from a 1 to a 2. One of the sugar water potatoes was the only potato to have dark discolored water; all the other potatoes had yellowish water if it was discolored.
Investigation Theme PGST
Grade Level High School Students (Grades 9,10,11,12)
School Name California Academy of Mathematics and Science
Session Fall 2020
About this Project

The students did a great job of making update posts often. These posts were all well thought out and full of details. The mentor was very active and responded quickly to each post. They had great communication and were able to bounce ideas off of each other.
-- Jessica Prosser, Scientist Liaison