On average, 25 billion styrofoam cups are thrown away each year just by Americans—that is about 82 per person. Styrofoam is made of expanded polystyrene foam, a very chemically inert substance that is resistant to many acids and bases. Made up of 98% air, styrofoam is used in all sorts of things such as cups, packaging and insulation. Polystyrene is very slow to biodegrade, taking hundreds of years to breakdown. The pollution from styrofoam is a large environmental concern due to polystyrenes high resistance to chemicals, long biodegrading time, and overproduction ( over 14 million polystyrene produced each year around the world).
Our goal is to isolate the bacteria in mealworms that work to digest styrofoam and then genetically engineer that bacteria to only digest styrofoam so that it digests quicker. Our hypothesis is that the bacteria in the mealworms will digest the styrofoam more efficiently and effectively than the mealworms.
Scientists Jun Yang and Lei Jiang from Beihang University, in Beijing tested mealworms and their ability to digest styrofoam. They "...isolated 13 bacterial cultures from the guts of the mealworms and grew them on polystyrene film. The most abundant was a strain of Exiguobacterium." In order to extract Exiguobacterium from a mealworms, we would dissect a mealworm and spread the contents of the gut onto a piece of styrofoam. After a day or two we would transfer the gut onto a new piece of styrofoam. This would be repeated multiple times until the only living organism left is the styrofoam eating bacteria because styrofoam is the only available food source. If Exiguobacterium is an anaerobic bacteria, we could transfer the bacteria into an aerobic organism so that the new organism can do the same job.
Parts and Devices
We don’t have the parts because we are trying to find the parts for it within our bacteria. Ideally we would want an RBS that could make many copies of the enzyme, so the styrofoam would be broken down quicker. We would also want the promoter that can identify styrofoam because we would want the bacteria only to work in the presence of styrofoam.
Possible complications that can occur are: the bacteria that we saw under the microscope could only be decaying bacteria. The bacteria could also possibly be anaerobic, so we would have to figure out how to get growth with anaerobic bacteria. One other complication is that we can't find the enzyme, or the chassis that we pick won't take the enzyme. Another complication is that the anaerobic enzyme will not even function in any aerobic cell. During the development of the bacteria, employees would be required to wear safety equipment such as goggles, gloves, and aprons. The bacteria would have to have a “kill switch” so if it were released into the environment for any reason, it could be contained. The bacteria would be engineered to only survive in the presence of styrofoam so if it were to be released it would die without its only food source.
A group member, Deanna, was housing mealworms for two months prior to the experiment. Their only food source was styrofoam. The first trial consisted of cutting up small circular pieces of styrofoam and placing them in petri dishes. The styrofoam was scraped with a razor blade to allow water to absorb into the styrofoam with the intent that the bacteria doesn’t dry up. After water was spread on the styrofoam, we extracted the gut from the mealworms and spread them on the styrofoam. Since it was our first trial and an attempt to establish a basis for our future experiments, the tools we used were not sterilized. In order to extract the gut from the mealworms, they were placed on pieces of cardboard and their heads were detached. From there, the bodies were vertically cut and the gut was transferred onto the styrofoam using inoculation loops. The petri dishes with the styrofoam inside were sealed and placed in an incubator overnight and were examined the next day. In total we had four petri dishes to examine (trial 1).
After evaluating our procedure for the first trial, we brainstormed different ways to approach a new trial to test our hypothesis (trial 2). We took 2.5 grams of styrofoam and grinded it into 500 mL of water using a blender. The styrofoam and water solution that was created was then microwaved to sterilize it. After this, our group made agarose gels to grow the bacteria on. With a total of six petri dishes, three of them were with plain agarose and three of them had a styrofoam base (the styrofoam and water solution created). One petri dish with plain agarose and one petri dish with styrofoam was covered with E.Coli. We used fresh bacteria to cover a plain agarose petri dish and a petri dish with styrofoam. Finally, the remaining petri dish with plain agarose and styrofoam was covered with the farmed bacteria (the bacteria from the first experiment). The petri dishes were left for two day to grow and were then examined under a microscope. There was no growth on either of the E. Coli dishes, which is a good thing because that was our control. There was some growth on both styrofoam dishes, we are not sure whether it is decayed bacteria or the bacteria in question. The fresh bacteria on agarose did grow a little bit.