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- Herausgeber: John Wiley & Sons
- Kategorie: Lebensstil
- Sprache: Englisch
Discover the fundamentals of fungi with this engaging and easy-to-follow book
Fungi For Dummies gives you an in-depth view of the wide world of mycology. With this science-focused yet clear and readable book, you'll dig deep into the science of the fascinating organisms that help this planet thrive. Learn about fungi classifications and structures, their uses in and beyond medicine, their importance to environmental sustainability, and how they have shaped human cultures around the world. Go beyond the typical mushroom field guide and get a thorough introduction to the study of mycology that tracks a typical undergraduate course in the field.
- Grasp the basics of mycology, including how fungi grow and how they differ from plants
- Discover the role fungi play in ecosystems around the world
- Learn to classify the different biological structures that appear in fungi
- Know the various fungal groups and their roles in nature and in human endeavors
Perfect for those who want or need to get a grasp on mycology, Fungi For Dummies is an approachable introduction to this essential organism group.
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Seitenzahl: 390
Veröffentlichungsjahr: 2025
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Fungi For Dummies®
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Table of Contents
Cover
Table of Contents
Title Page
Copyright
Introduction
About This Book
Foolish Assumptions
Icons Used in This Book
Beyond the Book
Where to Go from Here
Part 1: Getting Started with Fungi
Chapter 1: Finding the Fungus Among Us
Appreciating the Power of Fungi in Nature
Exploring How Fungi Form Partnerships with Other Organisms
Taking a Close Look at Fungal Structures
Unlocking the History of Fungi
Discovering the Many Groups of Fungi
Making Connections Between Fungi and People
Chapter 2: Exploring the Role of Fungi in Nature
Why Fungi Aren’t Plants (and Never Were)
Decomposing the Dead
Parasitizing the Living
Making Connections in Communities
Chapter 3: Benefitting from Fungal Relationships
Exploring the Wood Wide Web
Living on the Edge: Lichens
Chapter 4: Examining Fungal Structures
Focusing on Fungi from the Cells Up
Starting with Spores
Weaving Through the World
Recognizing Different Species
Chapter 5: Reproducing the Fungal Way
Exploring Fungal Reproduction
Identifying Sources of Variation
Part 2: Diving Deeper Into Fungal Groups
Chapter 6: Mapping the Genetics of Fungi
Exploring the Genomes of Fungi
Examining Fungal Chromosomes
Mapping Chromosomes
Chapter 7: Digging Into the Origins of Fungi
Writing the Fungal Origin Story
Discovering Fossil Fungi
Looking for Ancestral Groups
Chapter 8: Swimming with Zoosporic Fungi
Reproducing with Zoospores
Living Off Others with the Opisthosporidia
Digesting the Tough Stuff with the Chytridiomycota
Ruminating with Neocallimastigomycota
Attacking Crops with the Blastocladiomycota
Chapter 9: Adapting to Life on Land with the Zygomycetous Fungi
Uniting the Zygospore-forming Fungi
Forming Mycelia with Zoopagomycota
Forming Arbuscular Mycorrhizae with the Glomeromycota
Getting Familiar with Mucoromycota
Exploring the Life Cycle of the Zygomycetous Fungi
Chapter 10: Morels, Yeasts, Mildews, and More: The Ascomycota
Discovering the Characteristics of the Ascomycota
Growing by Yeast and Hyphae with the Taphrinomycotina
Budding with the Saccharomycotina
Forming Ascocarps with the Pezizomycotina
Looking at the Life Cycle of the Ascomycota
Chapter 11: Portobellos, Puffballs, Stinkhorns, and More: The Basidiomycota
What It Takes to Be a Member of the Club
Recognizing Familiar Fungi in the Agaricomycotina
Generating Rusts on Plants with the Pucciniomycotina
Forming Smuts on Plants with the Ustilaginomycotina
Part 3: Putting Fungi to Use
Chapter 12: Fine Dining with Fungi
Feeding Ourselves with Fungi
Fermenting with Fungi
Chapter 13: Spiritual Uses of Fungi
Exploring Human Perceptions
Expanding the Mind with Magic Mushrooms
Chapter 14: Using Fungi as Medicine
Producing Antibiotics from Fungi
Exploring Traditional Uses of Fungi
Moving from Traditional Knowledge to Western Medicine
Chapter 15: Farming Fungi
Growing Mushrooms at Home
Looking at Commercial Production of Fungi
Part 4: The Part of Tens
Chapter 16: Ten Fantastical Fungi Tricks
Turning Ants into Zombies
Attracting Insects with Rotting Meat
Striking Fear in Mushroom Foragers
Absorbing Radiation
Living Underwater
Living Extra Large
Exploding into a Cloud of Smoke
Glowing in the Dark
Growing in an Ant’s Garden
Fighting Cancer
Chapter 17: Ten Ways We May Use Fungi in the Future
Breaking Down Plastics
Improving Biofuel Production
Using Mycorrhizae as Natural Fertilizer
Fighting Infections with New Fungal Compounds
Controlling Biofilms in Medical Settings
Improving Nerve Function
Eating More Fungal Foods
Cleaning Up Pollutants
Using Fungal Enzymes in Industry
Farming for the Future
Chapter 18: Ten Resources for Learning More About Fungi
The North American Mycological Association
Your Local Mushroom Club
The U.S. Centers for Disease Control and Prevention
FUNGIWOMAN
Websites
Podcasts
YouTube
Fungi-Friendly Books and Magazines
iNaturalist
Commercial Suppliers for Growing Fungi
Index
About the Author
Connect with Dummies
End User License Agreement
List of Tables
Chapter 6
TABLE 6-1 Beadle and Tatum Experiment
Chapter 7
TABLE 7-1 A Comparison of the Taxonomy of Several Species
List of Illustrations
Chapter 2
FIGURE 2-1: Mushrooms above the soil showing their masses of branching, thread-...
FIGURE 2-2: Drawing of a “hairy mold” colony (later identified as the mold
Muco
...
FIGURE 2-3: A phylogenetic tree of life based on comparison of rRNA genes.
FIGURE 2-4: The carbon cycle.
FIGURE 2-5: The greenhouse effect.
Chapter 3
FIGURE 3-1: Symbiotic associations between plants and fungi.
FIGURE 3-2: A comparison of ectomycorrhizae and endomycorrhizae.
FIGURE 3-3: Orchidaceous endomycorrhizae.
FIGURE 3-4: Lichens.
FIGURE 3-5: The organization of a heteromerous lichen thallus.
FIGURE 3-6: Oakmoss lichen,
Evernia prunastri,
is an example of a foliose liche...
FIGURE 3-7: The pixie cup lichen,
Cladonia asahinae,
is an example of a frutico...
FIGURE 3-8: Reindeer lichen,
Cladonia rangifera
.
Chapter 4
FIGURE 4-1: A fungal cell in the process of cell division.
FIGURE 4-2: The fluid mosaic model of the plasma membrane.
FIGURE 4-3: Aerobic cellular respiration in a eukaryotic cell.
FIGURE 4-4: The structure of the fungal cell wall.
FIGURE 4-5: Asexual spore formation in three types of mold.
FIGURE 4-6: An overview of reproduction in fungi.
FIGURE 4-7: Sexual spores in three groups of fungi.
FIGURE 4-8: The life cycle of a mushroom.
FIGURE 4-9: Fungal hypha with a close-up of the hyphal tip.
FIGURE 4-10: Septate and coenocytic hyphae.
FIGURE 4-11: Mushroom anatomy.
Chapter 5
FIGURE 5-1: Fungal life cycles.
FIGURE 5-2: The cell cycle in yeast.
FIGURE 5-3: An overview of meiosis.
Chapter 6
FIGURE 6-1: Deoxyribonucleic acid (DNA).
FIGURE 6-2: The one gene, one enzyme hypothesis.
FIGURE 6-3: Tetrad analysis in yeast.
Chapter 7
FIGURE 7-1: Fungal evolution based on the fossil record and DNA sequencing (Ma=...
FIGURE 7-2: Fungal phylogeny.
FIGURE 7-3: Reading a phylogenetic tree.
Chapter 8
FIGURE 8-1: Microsporidia.
FIGURE 8-2: Types of chytrid thalli.
FIGURE 8-3: The mycoloop.
FIGURE 8-4: An overview of the chytrid life cycle.
Chapter 9
FIGURE 9-1: The black bread mold,
Rhizopus stolonifer.
FIGURE 9-2: Spore release in the dung-fungus
Pilobolus.
FIGURE 9-3: Life cycle of a zygote-forming fungus (
Mucor
sp.).
Chapter 10
FIGURE 10-1: Examples of ascomycetes.
FIGURE 10-2: Types of ascocarps.
FIGURE 10-3: The life cycle of an ascomycete (
Peziza
sp.).
Chapter 11
FIGURE 11-1: Examples of basidiomycetes.
FIGURE 11-2: The basidiomycete life cycle.
FIGURE 11-3: A surface tension catapult.
FIGURE 11-4: Huitlacoche or corn smut caused by
Mycosarcoma maydis
infection of...
Chapter 12
FIGURE 12-1: Gut microbiota in the human digestive system.
FIGURE 12-2: The five basic tastes.
FIGURE 12-3: A variety of edible mushrooms.
FIGURE 12-4: Examples of different types of fermentation.
Chapter 13
FIGURE 13-1: The rabbit-duck illusion.
FIGURE 13-2: Some regions of the brain and their primary functions.
FIGURE 13-3:
Psilocybe cubensis
.
FIGURE 13-4: Psilocybin, psilocin, and serotonin.
FIGURE 13-5: Poisonous mushrooms.
Chapter 14
FIGURE 14-1:
Penicillium
and penicillin.
FIGURE 14-2: Zone of inhibition.
FIGURE 14-3: Medicinal mushrooms.
Chapter 15
FIGURE 15-1: Easy-to-grow mushrooms.
FIGURE 15-2: Some methods for home cultivation.
Guide
Cover
Table of Contents
Title Page
Copyright
Begin Reading
Index
About the Author
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Fungi For Dummies®
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Library of Congress Control Number: 2025946196
ISBN 978-1-394-34483-3 (pbk); ISBN 978-1-394-34485-7 (ebk); ISBN 978-1-394-34484-0 (ebk)
Introduction
Fungi may be the most mysterious and powerful organisms on the planet. Most of the time, they grow almost invisibly through the soil below your feet, decomposing plant matter. When environmental conditions are right, some of them make their presence known, exploding in a sudden profusion of colorful mushrooms. Many people around the world have appreciated the visible fungi for thousands of years, benefitting from their excellent nutritional qualities and powerful chemicals. Other people are newer members of the fungal fan club, attracted by new flavors, a desire to live more sustainably, or even just a longing to probe the secrets behind the mushroom. This book is about the ways fungi make all life possible and how they can make it better.
About This Book
Fungi For Dummies is an introduction to the world of fungi and their role in ecosystems. A special emphasis is placed on their importance to people. My goal is to provide the fundamentals of fungal structure and life history that you could apply to either the academic study of fungi or a personal interest in foraging or growing mushrooms. Depending on your personal background, this book may contain surprises about the importance of fungi to agriculture, medicine, or spirituality.
The table of contents highlights the modular organization of the book, which makes it easier for you to find the sections most useful to you. I present some fungal fundamentals in the first part of the book, then dive into some more technical details in the second part. The third part showcases some of the ways people use fungi, and the last part hits some of the highlights of why fungi are so cool.
Foolish Assumptions
As I wrote this book, I tried to imagine who you are and what type of information you are looking for. Here’s what I came up with:
You may be someone who became interested in fungi because of their beauty and wants to know more about them. The chapters at the beginning and end of the book will fill you in on the fundamentals and the ways fungi are relevant to your life.
You may be someone who loves the flavors of fungi and wants to learn more about foraging or growing your own. There’s a chapter on fungal structures to get you started on learning to identify fungi and a chapter that introduces you to growing fungi on your own. I’ve also provided suggestions for resources you can turn to when you’re ready to take the next step.
You may be an experienced forager who would like to learn more about the scientific details of how fungi grow. If you have never had formal academic training on fungi and would like to know what you missed, the middle of the book is for you.
You may be a college biology major studying botany as part of your year-long freshman series or a student in an introductory mycology course. The beginning and middle of the book will fill you in on the fungal structures and life cycles that you’ll need to know for class.
Icons Used in This Book
Throughout this book, icons in the margins highlight certain types of valuable information that call out for your attention. Here are the icons you’ll encounter and a brief description of each.
The Tip icon lets you know what you need to do to get to the heart of the matter at hand. These icons mark information that helps you remember the facts being discussed or suggest a way to help you commit them to memory.
Remember icons mark the information that’s especially important to know. To siphon off the most important information in each chapter, just skim through these icons.
The Technical Stuff icon marks information of a highly technical nature that you can normally skip over.
The Warning icon tells you to watch out! It marks important information that may save you headaches. I’ll use this icon to let you know which old names for fungal groups are no longer being used, and which subjects are still under investigation.
Beyond the Book
In addition to the abundance of information and guidance related to fungi that I provide in this book, you get access to even more help and information online at Dummies.com. Check out this book’s online Cheat Sheet, which provides a few concepts to get you started on your journey into the world of fungi and their role in Earth’s ecosystems. Just go to www.dummies.com and search for “Fungi For Dummies Cheat Sheet.”
Where to Go from Here
Like all For Dummies books, each chapter in Fungi For Dummies is self-contained, so you can pick it up whenever you need it and jump into the topic you are working on. You can start reading this book in whatever part interests you the most. If you want to know about the basic structures of fungi, how they grow, and their importance to ecosystems, you can start at the beginning. If you’re more interested in how people use fungi, you can begin at the end. And if you’re a student in a biology class, or just someone who wants to get into the finer details of different types of fungi, you can jump to the middle. Wherever you are, I’ll give you tips about other places in the book that connect to what you’re reading.
I hope you enjoy your journey into the world of fungi and find them as fascinating and beautiful as I do!
Part 1
Getting Started with Fungi
IN THIS PART …
Explore the diversity of Kingdom Fungi, from the mushrooms you see in the forest, to the yeast that’s used to make bread and wine, to the fuzzy green mold that grows on old oranges, and many more you may not even notice.
Discover the role fungi play in nature and the important role they play in decomposition.
Take a look at how fungi partner with other organisms to help them grow.
Examine fungi at a cellular level and consider the features that make them unique among living things.
Explore how fungi reproduce and change their DNA over time.
Chapter 1
Finding the Fungus Among Us
IN THIS CHAPTER
Discovering the importance of fungi in nature
Exploring the diversity of fungal groups
Brushing up on the benefits of fungi
Kingdom Fungi includes everything from the mushrooms you see in the forest or the grocery store, to the yeast that’s used to make bread and wine, to the fuzzy green mold that grows on old oranges, and many more you may not even notice. Fungi can be mysterious, suddenly appearing as a “fairy circle” in the forest. Some fungi are a little spooky, like the ones that turn ants into zombies or those that glow in the dark. Fungi can be beautiful too, like the fly agaric with its bright red cap and white spots (Amanita muscaria) or the veiled lady (Phallus indusiatus) shown on the cover of this book.
These weird and wonderful fungi lead secret lives beneath the surface of the soil or within the bodies of other organisms. They are essential to the cycle of life on Earth, and many can directly harm or benefit human health. This chapter introduces you to fungi and gives you a peek into what is happening below the surface of the fungal structures you can see.
Mycology is the study of fungi, including their structure, role in nature, life cycles, and chemistry (myco=fungus, logy=study of).
Appreciating the Power of Fungi in Nature
Organisms interact with each other and their environment in complicated webs called ecosystems. For example, you’re probably familiar with the way organisms interact in food chains. A food chain represents the movement of energy and nutrients through a series of organisms. For example, a mouse eats seeds, and then a snake eats the mouse.
When one organism eats another, it takes in the large molecules like carbohydrates, proteins, and fats that form the bodies of living things. It digests these large molecules into smaller components, taking the energy and nutrients it needs for its own growth. The molecules that make up one living thing get broken down and reformed into the molecules of another. If you eat a slice of pizza, you will essentially recycle some of the pizza molecules to build or repair your own body. (Yes, in some ways, you are what you eat.)
While all organisms pass nutrients through food chains, fungi are nature’s ultimate recyclers. They make enzymes that can digest the really tough stuff like wood that few other organisms can touch (for details on how fungi break down wood, see Chapter 2). And they’re not squeamish. They don’t need their food to be alive or even freshly killed. In fact, they’re specialists in digesting the dead.
Decomposers digest dead organisms, breaking down their large molecules into smaller components. In the process, they release nutrients like minerals and carbon dioxide (CO2) back into the environment where they can be picked up and reused by other living things (see Chapter 2 for more details on how carbon moves through ecosystems).
The molecules that make up living things are a type of matter. Matter is anything that has mass (can be weighed) and takes up space. It’s the stuff that makes up everything around you, from the metal atoms in your cell phone to the cellulose that forms the paper in this book. Except for the occasional meteorite that hits the surface of the planet, no new matter enters our environment. (Light from the sun is energy, not matter.) All of the matter that makes up our planet and living things must be recycled if life is to continue.
Without decomposers like fungi and bacteria, there wouldn’t be enough matter available for the growth of new life.
Exploring How Fungi Form Partnerships with Other Organisms
Many fungi form intimate relationships that facilitate the growth of other organisms.
Mycorrhizal fungi attach to plant roots and grow outward through the soil in vast networks. In exchange for food, the mycorrhizae increase the access of plants to water and minerals (Chapter 3). Experiments suggest mycorrhizae can even enable communication between plants over their mycelial network. Almost all plants, including those we grow for food, have mycorrhizal partners that support their growth.
Fungi also form partnerships with other photosynthetic organisms, like algae and blue-green bacteria, becoming lichens that grow on the surfaces of rocks, plants, and soil.
Lichens are plant-like growths that form from the symbiosis of at least two organisms, a fungus and a photosynthetic partner (Chapter 3).
The fungal mycelium provides a protective covering for its partner, storing water and blocking intense light. In return, the alga or bacterium shares some of the food it makes through photosynthesis.
Taking a Close Look at Fungal Structures
The parts of fungi that you can see are just a tiny fraction of the entire organism. When you see a mushroom, for example, you may think you’re looking at a single individual, but what you’re actually seeing is the reproductive structure of a massive organism that’s growing beneath the mushroom.
Fungi grow as barely visible threads called hyphae that weave through soil and decaying organisms (Chapter 4).
Hyphae are long chains of fungal cells that grow and weave themselves throughout their environment, forming mats called mycelia. Sometimes, fungi shape their mycelia into large reproductive structures like mushrooms, bracket fungi, or puffballs. Examining the details of structures like these can help you identify wild fungi.
The reproductive structures of fungi produce spores, which are special cells that protect the genetic information of a new individual (Chapter 4). Fungi can clone themselves by producing spores asexually, or they can produce spores after a sexual process that combines genetic information from two individuals. The spores found among the gills on the bottom of a mushroom or in the pores of a bracket fungus are examples of sexually produced spores.
Unlocking the History of Fungi
Fungi have an interesting life cycle, which makes them useful organisms for the study of genetics (Chapter 6). The cells that form fungal hyphae are haploid, meaning they only have one copy of each gene. This makes it easier to study the effects of mutations on genes in fungi than it is in other organisms, like plants and animals, which typically have two copies of each gene.
Scientists think the first fungi lived in the water, then made their way onto land around the same time as plants, although they’re still debating the exact order of events (Chapter 7). Scientists haven’t studied many fossils of fungi, but some fossils that resemble modern aquatic chytrids (Chapter 8) can be dated to the late Precambrian period (650 to 543 million years ago). Fossils from the Devonian period (417 to 354 million years ago) show land plants and fungi forming symbiotic associations similar to today’s mycorrhizal associations. In fact, some scientists believe that plants wouldn’t have been able to move from the water to the land without the help of fungal partners.
Discovering the Many Groups of Fungi
The ability to read and compare the DNA of organisms caused many changes to the way scientists see the relationships between life on Earth. Prior to the development of DNA science, scientists classified organisms based on their physical characteristics, how they got their nutrition, and how they reproduced. These methods worked well for many larger species, but microscopic organisms with few visible characteristics were harder to sort out.
As a result, scientists have made many recent changes to the organization of the fungi. Some organisms that we thought were closely related to fungi, because of the way they look and grow, were kicked out of the kingdom. Relationships within the kingdom changed, and some fungi were moved from one group to another. And some fungi that never did scientists the courtesy of showing their sexual stages so that they could be sorted were finally put in their place on the basis of their DNA. Finally, the vast majority of fungi that grow in nature haven’t been identified at all, so more changes to our understanding of the relationships of fungi to each other and other organisms will no doubt occur in the future.
Whether they are true fungi or not, these groups of organisms are commonly included in the science of mycology:
Stramenopiles
include the water molds (oomycetes) and slime nets (labyrinthulomycetes). Both of these groups were originally included in Kingdom Fungi because of their fungal-like lifestyles.
Amoebozoa
are the slime molds, amoebae that can often be found along with fungi growing on rotten logs. Also like fungi, they reproduce by spores and are important decomposers.
Opisthosporidia
are intracellular parasites that don’t have much surface resemblance to fungi, but whose DNA reveals a very close relationship (
Chapter 8
).
Chytridiomycota,
also known as chytrids, are swimming single-celled organisms that decompose organic matter and have chitin in their cell walls. These characteristics, along with their DNA, put them in the fungal kingdom (
Chapter 8
).
The
zygomycetous fungi
include many of the familiar molds you’ve seen growing on your cheese, bread, and spoiled fruit (
Chapter 9
).
The
Ascomycota
is important to human food production because this group contains yeast, morels, and truffles, as well as some plant pathogens known as mildews (
Chapter 10
).
The
Basidiomycota
is the home for most of the familiar mushrooms as well as plant pathogens known as rusts and smuts (
Chapter 11
).
Making Connections Between Fungi and People
In addition to their importance to the health of the planet, fungi have many direct impacts on the lives of people:
Food:
Fungi are not only delicious, but they’re also packed with beneficial nutrients such as dietary fiber (
Chapter 12
). Plus, research shows they have a positive impact on your brain and immune system and contain compounds with many potential health benefits (
Chapter 14
).
Spiritual uses:
Some cultures past and present use psychedelic mushrooms in their spiritual practices (
Chapter 13
). Doctors today are exploring the use of these mushrooms to benefit mental health.
Medicine:
The first antibiotic used to fight human infections was called penicillin after the
Penicillium
mold that makes it (
Chapter 14
). Today, scientists are testing fungi like turkey tail (
Trametes versicolor
) for their ability to fight cancer and using fungi to produce cholesterol-lowering statin drugs.
Chapter 2
Exploring the Role of Fungi in Nature
IN THIS CHAPTER
Defining fungi
Discovering the importance of decomposition
Exploring the impact of fungi on the living
If you look at a forest or a field, you probably notice the plants and maybe some animals. If you look closely, you may also see a few fungi, like shelf fungi growing on a tree or some mushrooms sprouting up through the grass. What you don’t see is what is happening below the surface of that forest or field. Woven throughout the soil are the fine threads of growing fungi, making up as much as 90 percent of the living component of the soil by weight. These threads are busy absorbing water and digesting organic matter. Some of them even form partnerships with the plant roots around them. Fungi are in the environment all around us, but they often go unnoticed until they make a larger reproductive structure like a mushroom. This chapter presents what fungi are, as well as what they aren’t, and takes a look at some of the ways they impact life on Earth.
Why Fungi Aren’t Plants (and Never Were)
It’s easy to understand why people might think fungi are plants. The visible fungi, such as mushrooms, form structures that don’t seem to move or make noise, and they’re often found growing among or even on plants. You can even walk up and pick a mushroom just like you’d pick a flower.
Today, the term mushroom most often refers to the large, fleshy, reproductive structure of a fungus. This definition would include both the classic umbrella-shaped fungi and the shelf-like bracket fungi that you sometimes see growing on the side of wood. However, some scientists use an older, more restrictive definition of mushroom that only refers to the umbrella-shaped reproductive structure (also known as the fruiting bodies).
Appearances, as they say, can be deceptive. Even though fungi might look like plants, when scientists compared fungal DNA to that of other living things, they found that fungi are more closely related to animals (including you and me) than they are to plants. This wasn’t a complete surprise to scientists, though, because when you look below the surface, you learn that the fungal lifestyle is very unlike that of plants.
Absorbing food from others
One of the biggest differences between fungi and plants is the way fungi get their food. Plants do photosynthesis, using energy from the sun to combine carbon dioxide and water to make sugars. Fungi get their energy and matter like we do by eating food.
Plants are autotrophs (auto=self, troph=feed), which means they make their own food. Fungi are heterotrophs (hetero=other) because they must eat food that was originally made by other organisms.
Although fungi and animals are both heterotrophs, most fungi grow by microscopic threads called hyphae, like those shown in Figure 2-1. Hyphae grow and branch, forming a woven mass called a mycelium that makes up the body of the fungus. The fungal cells that form the hyphae have rigid cell walls. Because of their small size and cell walls, fungi can’t ingest or engulf large food particles. (For more details on hyphae and fungal cell walls, check out Chapter 3.)
designua/Adobe Stock Photo
FIGURE 2-1: Mushrooms above the soil showing their masses of branching, thread-like hyphae growing through the soil.
Fungi are absorptive feeders. They weave their hyphae through their food, releasing digestive enzymes outside of their cells. These exoenzymes help break large molecules down so that the fungi can absorb the smaller components into their cells.
In other words, if fungi were people, they’d be doing digestion all over the surface of their skin instead of inside their digestive systems. If you’ve ever seen a piece of fruit turned to watery mush by a mold, you’ve seen fungal digestion in action.
Creating a kingdom for fungi
People have been aware of and using fungi for thousands of years. People in Central America carved stones into mushroom shapes as early as 1000 BCE (Before Common Era), and edible mushrooms appear in art from the ruined city of Pompeii that dates to 79 CE. Books written on herbals during the Middle Ages contain descriptions and uses for both plants and fungi. But although people were using fungi for food, medicine, and spiritual rituals, they didn’t really know what fungi were or where they came from. Some people saw them as plants, while others thought they had a supernatural origin. Several ancient cultures, for example, thought mushrooms appeared after thunderstorms.
The invention of the microscope led to more detailed studies of the structure of fungi. In 1665, an English doctor named Robert Hooke published a book of drawings that included the drawing of a mold as he saw it through a microscope (see Figure 2-2). His drawing shows hyphae and round structures called sporangia that contain spores, which are the reproductive cells of fungi.
Over the next few hundred years, scientists advanced their understanding of the genetics and reproduction of fungi, but most of them still put fungi in the same category as plants. It wasn’t until 1969 that Robert Whittaker proposed that the fungal lifestyle was so different from that of plants that they needed their own category, which he called Kingdom Fungi. Whittaker placed fungi into their own kingdom because of their important role in breaking down dead organisms in the environment, their unique cellular structures, and the fact that they are heterotrophic, absorptive feeders. He also noted that most fungi are multicellular.
FIGURE 2-2: Drawing of a “hairy mold” colony (later identified as the mold Mucor) published by Robert Hooke in 1665.
The study of fungi is called mycology (myco=fungus, logy=study of).
Mycologists and other scientists use several different terms when describing fungi:
Fungus
(or plural fungi) refers to all organisms within Kingdom Fungi.
Mold
is a descriptive term that refers to things that grow as multicellular filaments.
Mildew
refers to molds that grow on surfaces such as walls. Neither of these terms indicates a specific species or relationship.
Yeast
is a descriptive term for fungi growing as single cells. Some fungi can switch between growing as a yeast to growing as a mold.
Since the 1960s, comparisons of DNA sequences between organisms have confirmed that fungi are distinct from plants and are actually more closely related to animals. Scientists often compare the genes for a molecule called ribosomal RNA (rRNA) to examine relationships between organisms. All cells have rRNA, so it’s possible to use these comparisons to build a tree of all life on Earth, like the one shown in Figure 2-3, where groups of different types of organisms are shown as branches. Scientists use computers to draw the trees so that the physical distance along the branches represents the relationship between groups. The closer the two branches are, the closer the relationship.
Kingdom Fungi belongs to a large category of organisms called Domain Eukarya. This domain also contains the kingdoms Plantae (plants) and Animalia (animals), as well as many groups of microorganisms. All members of Domain Eukarya have similar cellular structures, which are discussed in Chapter 4.
Scientists are still working to understand the relationships between organisms within the fungal kingdom and to sort out the relationships between fungi and other closely related organisms. This effort is complicated by the fact that we’ve only identified a very small fraction of the fungi on our planet.
FIGURE 2-3: A phylogenetic tree of life based on comparison of rRNA genes.
Scientists have identified about 150,000 different species of fungi, but they estimate that somewhere between 2.2 and 3.8 million species exist on Earth.
Fungi spend most of their lives growing microscopically, which is part of the reason that so few have been discovered and named. With so many species yet to be studied, it’s likely that our understanding of the relationships between fungal groups will continue to change in the near future. In the meantime, mycologists will continue to study both fungi and fungal-like organisms.
Decomposing the Dead
Fungi may be the most underappreciated life form on Earth. They work quietly all around us, breaking down the bodies of the dead. Without them, we’d be surrounded by piles of every leaf that ever fell, every animal that ever died. (Imagine how quickly your home would fill up with trash if the garbage collectors stopped coming.)
Most fungi are decomposers, organisms that break down dead material as a source of food. Scientists also refer to them as saprobes or saprophytes because they live on and break down decaying organisms.
Some people think that the dead just break down or that worms and insects eat the dead. Dead bodies would not decompose without the action of decomposers like fungi and bacteria. Mummies or preserved bog people demonstrate that — if you block microbial decomposition (with chemicals or an acid environment) — bodies do not decompose. When an organism dies, bacteria and fungi begin the decomposition process. If the dead organism is an animal, the smell of decay attracts insects like blow flies and beetles that lay their eggs in the corpse. The eggs hatch, and the larvae feed on the decaying corpse. So, while insects are important contributors to the decay of some organisms, they are considered scavengers because they are animals that eat the dead.
Employing enzymes
Fungi are absolute rock stars when it comes to breaking things down. They produce a wide variety of digestive enzymes, enabling them to break down complex molecules into their component parts. These include enzymes similar to those made by your own digestive system, such as lipases to break down fats, proteases to break down proteins, and amylases to break down starch. Fungi take digestion even further with enzymes that break down the tough molecules found in plant cells, allowing them to digest materials that other organisms can’t, like wood.
Enzyme names typically end in -ase and often refer to their function. For example, amylose is a type of starch, so amylase is an enzyme that breaks down amylose.
People use fungal enzymes for industrial processes, such as the production of paper, textiles, and biofuels. In fact, more than half of the enzymes used in industry today come from fungi. (For more on the use of fungi in biofuel production, head to Chapter 12.)
Plants produce a strong layer around their cells called a cell wall that can be difficult for other organisms to digest. In fact, you’ve probably heard of plant cell wall materials referred to as the fiber in your diet that passes through your digestive system without being broken down. When fungi find these fibers in animal feces or dead plant material, they represent an excellent source of energy and building materials:
All plant cells produce a
primary cell wall
that is flexible and surrounds growing cells. Primary walls contain the complex carbohydrates cellulose, hemicellulose, and pectin.
Some plant cells produce a
secondary cell wall
that is thicker and stronger than the primary cell wall. Secondary cell walls contain lignin in addition to cellulose and hemicellulose. Lignin is a complex branching molecule made up of alcohol subunits. It is what gives strength to plant cells, such as those found in wood.
Lignin
is a complex web of alcohol subunits.
It’s what gives wood its tough, rigid nature. Surrounds the cellulose and protects it from microbial decay.
Wood is one of the most amazing materials in nature. It’s a complex mixture of several types of molecules, but the main components are cellulose, hemicellulose, and lignin. It’s sturdy, rigid, and resistant to decay, which is why so many groups of people learned to use it for building material. For fungi, it presents an interesting problem because the useful carbohydrates are locked behind a wall of protective lignin.
Some fungi have developed strategies to deal with the lignin problem:
Fungi that cause
white rot
tackle the lignin head-on, breaking it down with enzymes called peroxidases. They almost totally break down wood, turning the wood white as they first digest lignin and then attack the cellulose. Wood decomposing by white rot turns white and often appears stringy or spongy.
Fungi that cause
brown rot
have developed a much more subtle approach. They use small ions (charged particles) to loosen the lignin and then sneak the carbohydrates out. They leave the lignin behind, causing the decomposing wood to appear dark brown and crumbly. If you’ve ever been hiking and reached out to touch a decaying tree stump and had pieces just break off in your hand, you were probably seeing the remains of brown rot.
Recycling carbon
The importance of fungi as decomposers isn’t just about the clean-up of life’s trash; it’s about their importance as master recyclers. As fungi decompose the remains of the living, they release nutrients back into the environment for living things to use again. They break down the fats, proteins, carbohydrates, and DNA from the dead, using what they need for energy and building materials and releasing the things they don’t need as waste. Fortunately for the rest of life on Earth, this means they release necessary nutrients like nitrogen and phosphorus back to the soil and carbon back to the air.
Scientists track the movement of the elements essential to life, noting how they change forms as they pass through living things and the environment. They call these pathways biogeochemical cycles to represent the fact that the elements (chemicals) move through the living (biotic) and geological components of ecosystems.
The carbon cycle, shown in Figure 2-4, may be the most important biogeochemical cycle on Earth. Not counting water, carbon is the most abundant element in living things. It makes up the backbone of all of our big molecules: carbohydrates, proteins, lipids like fats, and nucleic acids like DNA. To build new molecules, cells, and organisms, living things need a source of carbon. Plants and other autotrophs can capture carbon dioxide out of the environment and turn it into the molecules that everyone else needs, but if we didn’t have decomposers like fungi and bacteria, all of that carbon would eventually get locked up in the bodies of the dead. It’s the decomposers that eat the dead, returning carbon to the air as carbon dioxide.
Photosynthesis and cellular respiration are two of the most important processes that affect the carbon cycle:
During
photosynthesis,
autotrophs use energy from the sun to combine carbon dioxide (CO
2
) and water (H
2
O) into carbohydrates like glucose (C
6
H
12
O
6
). Oxygen gas (O
2
) is produced as waste.
During
cellular respiration,
organisms use oxygen gas (O
2
) to break down glucose (C
6
H
12
O
6
), capturing usable energy and producing carbon dioxide (CO
2
) and water (H
2
O) as waste.
danylyukk/Adobe Stock Photo
FIGURE 2-4: The carbon cycle.
The summary reaction for photosynthesis is 6 CO2 + 6 H2O + light energy → C6H12O6 + 6 H2O. The summary reaction for cellular respiration is C6H12O6 + 6 H2O → 6 CO2 + 6 H2O + energy.
Although most organisms perform cellular respiration to break down food molecules, releasing some CO2 back into the environment, the cellular respiration performed by fungi and bacteria during decomposition is essential to retrieving the carbon from the dead.
Sometimes people think that when decomposers break down the dead, they release carbon back into the soil. While some mineral forms of carbon can be found in the soil, this is not where plants get their carbon, nor is it how decomposers release carbon back into the environment. Decomposers release carbon as carbon dioxide back into the atmosphere, and plants reclaim it from there.
