Ask a Scientist: Beetles and Bacteria

Stealthy Shrimp asks, “How do bacteria take over a beetle’s body?

Great question, Stealthy Shrimp! To answer this question, we should first think about the different relationships bacteria can form with beetles (and with insects in general). Some of these relationships are beneficial for both sides, while other relationships are only beneficial for one side. Relationships where both sides work together and benefit are called mutualisms. For example, you have a healthy mix of bacteria that already lives in and on your body! This is called your microbiome. We get this bacteria from our mothers at birth, our food, the environment we live in, and from other animals. It may seem gross to have this bacteria all over, but it is important for keeping you healthy! Beetles also have a microbiome which keeps their bodies healthy in a number of ways, including defending against unhealthy, invading bacteria.

Other relationships where only one side benefits are called parasitisms. In these relationships, one organism benefits at the expense of the other. For example, a mosquito benefits from snacking on our blood, but we lose some blood (and sometimes get itchy–ouch!). For a parasite to take over a beetle’s body, the bacteria needs to get past the beetle’s defenses, including its healthy microbiome. The three main defenses the beetle has are its outer shell, the bacteria-fighting parts in its blood, and special protein-fighters that attack any bacteria that passes the first two defenses. If the parasitic bacteria can get past all three of the beetle’s defenses, the bacteria wins! The bacteria is free to grow in the beetle, hurting the beetle in the process. Stay curious and keep asking questions, Stealthy Shrimp!

– Nicole, the insect scientist

If you’re curious about other types of insect takeovers, check out this video of a parasitic fungi that attacks ants!

Main image [Source]: Tortoise beetle on a leaf.

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