What are fungi?

What are fungi?

Fungi are a domain of eukaryotic life on earth, separate from plants, animals, and protists. To the surprise of us all, scientists found that fungi are more closely related to animals than plants[1]! (Fun fact: this makes targeting fungal diseases in animals quite difficult.) They are similar to us in one major way- they are heterotrophs, meaning they don't make their own energy like plants do, so they need to consume nutrients for energy, like us. But the funny thing is that they do their digestion on the outside of their bodies, so I like to imagine little strands of the fungus vomiting acid onto the bit of space in front of them and then absorbing that nutritious hot mess. Indeed, it's a bit more like this:

This brings us to their structure! What do fungi look like?? The main body is actually underground, made of branching filaments called hyphae that together form an ever-growing network called mycelium. Seasonally, certain groups of fungi will pop up for a few days as a mushroom to spread their spores.

How do mushrooms grow? Instead of seeds, they grow out of spores. Spores are released into the air,  hopefully find a good place to grow (soil, living wood, dead wood, sand, dung, the forlorn food in the back of your fridge), hyphae filaments begin to grow (asexual, vegetative growth), when a hypha of the opposite sex is found they will fuse, the mycelium will continue to grow, upon favorable (rainy) conditions the mycelium will fruit, the fruiting body (mushroom) will release spores. The variety of forms that mushrooms take are staggering, and so this blog is born! Just know that they don't all look have the stereotypical umbrella shape as shown here.

But missing in this life cycle are the friendships made along the way. Almost all the plants in the world associate with fungi in the soil to the benefit of both parties. These mutualistic root-fungi complexes are known as mycorrhizae. 

Now not all fungi form mushrooms in their life cycle. In fact, having a mushroom stage is an uncommon, advanced, more recent evolution, the same way flowering plants are. Its always the newer fancy model that gets used to represent a much larger, diverse group of organisms. Fungi can be classified first into these two broad groups:

1. Arbuscular Mycorrhizal Fungi (AMF) - Asexually reproducing, does not fruit (mushroom). Associates with ~90% of the plant kingdom

2. Ectomycorrhizal Fungi (EMF) - Sexually reproducing, has a fruiting stage. Associates with ~5% of the plant kingdom, mostly conifers and deciduous hardwoods.

Now you know the basics of what fungi are. But it only gets more fascinating...what do fungi do?

[1]    Wainright, P.O., Hinkle, G., Sogin, M.L. and Stickel, S.K. The Monophyletic Origins of the Metazoa; An unexpected evolutionary link with Fungi. Science 260:340-243 (1993)