What is SYMBIOSIS? Episode 3: inside the pea aphid Let’s cover some of the vocabulary in the movie. This slide presentation can be shown before or after the third short film. For convenience, a link to all of the films is embedded in the last slide presentation. All photos used with permission from Day’s Edge Productions

Symbiosis is a relationship between two different species Symbiosis is a relationship between two different species. There are three main types of symbiosis. Symbiosis can benefit both organisms, it’s called mutualism. Or it can benefit one organism and harm the other parasitism. It can also benefit one organism and does not benefit or harm the other commensalism.

This partnership helps both partners. The movies focus on mutualism. It’s a partnership between two or more species. This partnership helps both partners.

This movie focuses on the symbiosis relationship between pea aphids and the bacteria that live in their gut.

What are Amino Acids? Amino acids are the building blocks of protein. Proteins make up a living thing’s cells, skin, hair, etc. They are the building blocks of your body. The amino acids a living thing can make on its own are called non-essential amino acids. The amino acids a living thing must get from its food are called essential amino acids.

DNA is a large molecule found in all living things DNA is a large molecule found in all living things. It directs how the cells build proteins out of amino acids with the help of RNA.

An explanation of the aphid/bacteria symbiosis The bacteria transform non-essential amino acids into essential amino acids for the aphid. The cell membrane receptors in the bacterial cells use transporter protein to allow the non- essential amino acid to enter and the essential amino acid to exit. These transporter proteins act like doors for the amino acids. When there is enough essential amino acids floating around, another protein called an inhibitor appears. Inhibitors are like guards that block the entrance into the bacterial cell. They block the opening of the transporter protein. The teacher can use slide 7 and 8 if he/she wishes to further explain this complex cellular process. This is also a possible extension for high school biology classes.

How does Dr. Wilson’s team figure out what the bacteria are doing for the aphid? Antibodies: proteins produced by a living thing’s immune system to recognize foreign particles like bacteria, viruses, and even pollen. Dr. Wilson’s team creates fluorescent antibodies that tag the transporters on the cell membrane of the bacterial cell. Green fluorescent tags (antibodies) can be seen on the cell membrane with the aid of a microscope.

Evolution is the process that explains that all living things on earth are related and descended from a common ancestor. Scientists look for patterns in nature. If other insects have the same type of symbiosis found in pea aphids, does that mean they share a recent common ancestor? If the symbiosis found in pea aphids is not found in similar insects, that leads to even more interesting questions.

Let's watch Symbiosis Episode 3 Inside the Pea Aphid To view all four films, click here