Hello! Thank you for subscribing to this limited run newsletter about the fascinating things fungi can do and how we can use them. My name is Silvia Hüttner, I'm a fungi enthusiast, a researcher specialised in fermentation and enzyme technology and I have a PhD in Industrial Biotechnology. I'd love to hear from you if you have any questions, comments or suggestions, or just want to say hi. 🍄
Imagine you’re in a forest. The sun trickles through the dense canopy of tall trees above you. You’re surrounded by plants and animals - birds chirping, woodpeckers pecking, leaves rustling, insects crawling. But there is another inhabitant in the forest, neither plant nor animal. It permeates the soft and bouncy soil under your feet with long, thin filaments, entangled and growing in all directions, decomposing dead wood into nutrients, nurturing tree roots. Here and there you can see a trace of this inhabitant, in the form of a shiny hat atop a delicate stem, a thick white wedge growing from the side of a tree trunk, or a velvet blanket covering a decaying fruit. Welcome to the world of fungi.
Fungi are a vital part of our ecosystems, often called the “recyclers of Nature”. But what exactly are these enigmatic lifeforms? They contribute to our lives in a myriad of ways, synthesizing antibiotics, acids and cholesterol medication, producing food and drinks, growing into furniture, insulation and clothes, cleaning water and decontaminating soil… Just like they permeate the forest floor, they permeate society, but still many people know very little about them. Most just view the creeping growth of mould as repulsive and disgusting, a sign of spoilage (though if watched closely, a quite beautiful one).
In this newsletter, I want to offer a different perspective. I’ll tell you stories where the fungi are the heroes. Fungi are a true cornerstone of our civilization, they deserve a place in the spotlight. 10 carefully selected topics will highlight the surprising and exciting ways in which fungi and fungal technology have changed, are changing, and will change our world.
“Fungi are diverse and often flexible, and they live in many places, ranging from ocean currents to toenails.” 
Fungi are neither bacteria, nor plant nor animal. But they share characteristics with all of these kingdoms, stretching conventional classification systems in a lot of ways.
Like bacteria, they can be classed as microorganisms—and some fungi do exist as microscopic single cells (yeasts). Most, however, exist as multicellular organisms—assembling into branching structures that cover centimetres or even metres in diameter.
Like plants, fungi can form different tissues and organs, and produce seed-like spores to spread. But unlike trees and flowers and algae, fungi don’t rely on sunlight to grow, and their cell walls don’t contain cellulose. Even so, until the middle of the 20th century, fungi were considered to be part of the plant kingdom and it was only after genetic analyses that we were able to determine for certain that they are actually related more closely to animals than to plants.
Like animals, fungi constantly need to find organic material to consume to stay alive. Animals usually do this by digesting food inside their bodies while fungi secrete digestive enzymes outside their bodies, directly onto their food, to break it down and then absorb this soup of nutrients. Animals usually move around, while fungi instead reach and grow in different directions (usually towards a food source).
Most fungi I will write about grow into vast networks (these are called “filamentous fungi”, or moulds), but I will occasionally mention and even dedicate a whole chapter to fungi that stay as single cells throughout their lives: the yeasts. Similarly, mushrooms will be mentioned at times, but there is a difference between fungi and mushrooms. Mushrooms are the fruiting bodies of some fungi, but not all fungi form mushrooms.
“A mushroom is not a self-contained organism, like a jellyfish, for example. It is a reproductive organ produced by a colony, or mycelium, which grows in soil or rotting wood. For convenience, we use the term ‘mushroom’ rather than ‘mushroom-forming fungus’ to describe the whole organism, although this is a bit like using a photograph of a large pair of testicles to represent an elephant.” 
The life of a filamentous fungus starts with a tiny spore, just a few micrometers in size, falling onto humid soil or a juicy fruit lying on the ground. The spore germinates and grows into a network of fine thread-like filaments (hyphae) that spread out and form the mycelium, a network of cells working together for survival, growing through organic matter, soil, wood and decaying leaves. Individual hyphae can only be seen under the microscope, but the mycelium as a whole grows into a large fluffy mass that is visible to the naked eye (like on that orange you forgot in the fruit basket).
Nutrients direct this growth, with the filaments acting as fine probing sensors that test the surrounding space and grow in whichever direction the conditions are more favourable. As they grow, the far tips of the filaments secrete enzymes into their environment that break down organic material into simple sugars, which are then taken up by the fungal cells and shared among the whole mycelium network.
“If you could make the soil liquid and transparent and walk into the ground, you would find yourself surrounded by the nets of fungal hyphae.” 
That’s as much fungal biology as you need to know for now, but it is important to set the scene for the three characteristics that are most important for understanding how humans use fungi:
Fungi are found almost everywhere on Earth - in soil, water, air, and on and inside other organisms. Recent estimates suggest that there are up to 3.8 million different species of fungi, of which only 120 000 have been formally recognised, and only 35 000 named . This means 97% of fungi are still waiting to be found, and most of those are in tropical parts of the world where species diversity is higher.
There are already a dizzying variety of fungi and mushrooms that have proven or supposed medicinal effects, can be eaten or are used for industrial processes. Imagine how many there are yet to be found. So let’s get to it.
In the next episode: Turning starch into protein. Eating mould. The history of Quorn. Fungi and the future of food production.
 The Mushroom at the End of the World. On the Possibility of Life in Capitalist Ruins. Anna Lowenhaupt Tsing, 2015. Princeton University Press.
 Mushrooms - A Natural and Cultural History. Nicholas P. Money, 2017. Reaktion Books Ltd.
 Fungal Diversity Revisited: 2.2 to 3.8 Million Species. David L. Hawksworth and Robert Lücking, 2018. The Fungal Kingdom. doi:10.1128/microbiolspec.FUNK-0052-2016