Symbiosis: Working together or not?
No one truly lives alone. Even if you don’t have housemates, you likely have a pet or a houseplant. Don’t have those either? No worries—you’re still accompanied by countless microbes throughout your life. We all have numerous symbiotic relationships, but what exactly is a symbiotic relationship?
Foto: microENVISION
What does symbiosis mean?
Symbiosis refers to a long-term interaction between two organisms. There are different types of symbiotic relationships, just as people collaborate in various ways. Think back to a group project—you’ve probably noticed that different people interact in different ways. Some collaborate and strengthen each other, while others take advantage of others' efforts. The same principle applies in nature; there are many kinds of coexistence, and it’s not always beneficial for everyone involved.
Stronger together
One type of symbiosis is mutualism, where both organisms benefit from the collaboration. A great example is our relationship with gut microbes. Our intestines host a vast number of microbes that help us digest fibers in our food. In return, we feed these microbes whenever we eat.
Mutualistic symbiosis is also seen elsewhere in nature. For instance, some deep-sea fish, like anglerfish, partner with bioluminescent microbes. The fish use the microbes’ light to hunt, while the microbes benefit by receiving a habitat and food from the fish.
Better off without
On the other end of the spectrum is parasitism, where one organism suffers from the other’s presence. A classic example is the relationship between humans and scabies mites. While the mites rely on humans to survive, their presence is far from pleasant for the host. Another striking example is the Cordyceps fungus. This fungus has many species, each targeting a specific insect. When an ant is infected, it becomes a zombie-like host controlled by the fungus. The ant climbs to a high point, clamps down so tightly it can’t let go, and eventually dies as the fungus grows through its body, sprouting a spore-bearing structure. It’s safe to say this is not a pleasant way of coexisting.
Together or alone?
Beyond mutualism and parasitism, there are other, less obvious forms of coexistence. One such type is commensalism, where one organism benefits while the other is unaffected. An example is a bird building a nest in a tree. The tree provides the bird with a safe place to nest, but the tree experiences no advantage or disadvantage from the bird’s presence.
Humans also host commensal organisms, such as the microbes on our skin. While some microbes are beneficial, there are also microbes we neither notice nor need. These microbes don’t harm us, but they benefit from having a place to live—our skin.
Human influence
In all these types of symbiosis, human activity significantly impacts ecosystems and, consequently, how organisms coexist. For example, pesticides are known to affect mycorrhizal fungi, which are crucial for plants they partner with. These fungi provide plants with additional nutrients from the soil in exchange for sugars produced by photosynthesis. When these fungi are harmed, the plants suffer too. Can you identify what type of symbiosis this represents after reading this blog?
Image of Cordyceps: Andreas Kay