Overview: Mighty Mushrooms Fungi are diverse and widespread They are essential for the well-being of most terrestrial ecosystems because they break down organic material and recycle vital nutrients

Fungi are heterotrophs that feed by absorption Despite their diversity, fungi share key traits, most importantly the way in which they derive nutrition Fungi are heterotrophs but do not ingest their food They secrete exoenzymes that break down complex molecules, and then they absorb the smaller compounds Fungi exhibit diverse lifestyles: Decomposers, parasites and mutualistic symbionts

Body Structure The morphology of multicellular fungi enhances their ability to absorb nutrients Fungi consist of mycelia, networks of branched hyphae adapted for absorption Most fungi have cell walls made of chitin Some fungi have hyphae divided into cells by septa, with pores allowing cell-to-cell movement Coenocytic fungi lack septa Some unique fungi have specialized hyphae that allow them to penetrate the tissues of their host

Reproductive structure Hyphae Spore-producing structures 20 µm Mycelium

Cell wall Cell wall Nuclei Pore Septum Nuclei Septate hypha Coenocytic hypha

Hyphae 25 µm Nematode Hyphae adapted for trapping and killing prey Plant cell wall Fungal hypha Plant cell Plant cell plasma membrane Haustorium Haustoria

Mycorrhizae are mutually beneficial relationships between fungi and plant roots Ectomycorrhizal fungi form sheaths of hyphae over a root and also grow into the extracellular spaces of the root cortex Endomycorrhizal fungi extend hyphae through the cell walls of root cells and into tubes formed by invagination of the root cell membrane

Fungi produce spores through sexual or asexual life cycles Fungi propagate themselves by producing vast numbers of spores, either sexually or asexually

Key Haploid (n) Heterokaryotic stage Heterokaryotic (unfused nuclei from different parents) PLASMOGAMY (fusion of cytoplasm) Diploid (2n) KARYOGAMY (fusion of nuclei) Spore-producing structures Zygote SEXUAL REPRODUCTION Spores ASEXUAL REPRODUCTION Mycelium MEIOSIS GERMINATION GERMINATION Spore-producing structures Spores

Sexual Reproduction Plasomogamy is the union of two parent mycelia In many fungi, the haploid nuclei from each parent do not fuse right away; they coexist in the mycelium, called a heterokaryon In some fungi, the haploid nuclei pair off two to a cell; such a mycelium is said to be dikaryotic

Hours, days, or even centuries may pass before the occurrence of karyogamy, nuclear fusion During karyogamy, the haploid nuclei fuse, producing diploid cells The diploid phase is short-lived and undergoes meiosis, producing haploid spores

Asexual Reproduction In addition to sexual reproduction, many fungi can reproduce asexually Many of these species grow as mold, sometimes on fruit, bread, and other foods

2.5 µm

Other fungi that can reproduce asexually are yeasts, which inhabit moist environments Instead of producing spores, yeasts reproduce asexually by simple cell division

10 m Parent cell Bud

Zygote fungi Arbuscular mycorrhizal fungi Sac fungi Club fungi Chytrids Chytridiomycota Zygomycota Glomeromycota Ascomycota Basidiomycota

Zygomycetes The zygomycetes (phylum Zygomycota) exhibit great diversity of life histories They include fast-growing molds, parasites, and commensal symbionts The zygomycetes are named for their sexually produced zygosporangia The life cycle of black bread mold (Rhizopus stolonifer) is fairly typical of the phylum

Key PLASMOGAMY 100 µm KARYOGAMY MEIOSIS Haploid (n) Heterokaryotic (n + n) Diploid (2n) PLASMOGAMY Rhizopus growing on bread Mating type (+) Gametangia with haploid nuclei Mating type (–) 100 µm Young zygosporangium (heterokaryotic) SEXUAL REPRODUCTION Dispersal and germination Zygosporangium (heterokaryotic) Sporangia KARYOGAMY Diploid nuclei Sporangium ASEXUAL REPRODUCTION MEIOSIS Dispersal and germination Mycelium 50 µm

Zygosporangia, which are resistant to freezing and drying, can survive unfavorable conditions Some zygomycetes, such as Pilobolus, can actually “aim” their sporangia toward conditions associated with good food sources

0.5 mm

Ascomycetes Ascomycetes (phylum Ascomycota) live in marine, freshwater, and terrestrial habitats The phylum is defined by production of sexual spores in saclike asci, usually contained in fruiting bodies called ascocarps Ascomycetes vary in size and complexity, from unicellular yeasts to elaborate cup fungi and morels

The cup-shaped ascocarps (fruiting bodies) of Aleuria aurantia give this species its common name: orange peel fungus. The edible ascocarp of Morchella esculenta, the succulent morel is often found under trees in orchards. 10 µm Tuber melanosporum is a truffle, an ascocarp that grows underground and emits strong odors. These ascocarps have been dug up and the middle one sliced open. Neurospora crassa feeds as a mold on bread and other food (SEM).

Ascomycetes reproduce asexually by enormous numbers of asexual spores called conidia Conidia are not formed inside sporangia; they are produced asexually at the tips of specialized hyphae called conidiophores

Key Conidia; mating type (–) Haploid (n) Dikaryotic (n + n) Diploid (2n) Dispersal Germination Mating type (+) ASEXUAL REPRODUCTION Mycelium PLASMOGAMY Ascus (dikaryotic) Mycelia Conidiophore Dikaryotic hyphae extended from ascogonium SEXUAL REPRODUCTION Germination KARYOGAMY Dispersal Diploid nucleus (zygote) Asci Eight ascospores Four haploid nuclei MEIOSIS Ascocarp

Basidiomycetes Basidomycetes (phylum Basidiomycota) include mushrooms and shelf fungi The phylum is defined by a clublike structure called a basidium, a transient diploid stage in the life cycle

Maiden veil fungus (Dictyphora), a fungus with an odor like rotting meat Fly agaric (Amanita muscoria), a common species in conifer forests in the northern hemisphere Puffballs emitting spores Shelf fungi, important decomposers of wood

In response to environmental stimuli, the mycelium reproduces sexually by producing elaborate fruiting bodies call basidiocarps Mushrooms are examples of basidiocarps The numerous basidia in a basidiocarp are sources of sexual spores called basidiospores

Dikaryotic mycelium PLASMOGAMY Mating type (–) Mating type (+) Haploid mycelia Gills lined with basidia SEXUAL REPRODUCTION Basidiocarp (dikaryotic) Dispersal and germination Basidiospores Basidium with four appendages Basidia (dikaryotic) Basidium Basidium containing four haploid nuclei KARYOGAMY MEIOSIS Key Diploid nuclei Haploid (n) 1 µm Basidiospore Dikaryotic (n + n) Diploid (2n)

Fungi have a powerful impact on ecosystems and human welfare Decomposers Fungi are efficient decomposers They perform essential recycling of chemical elements between the living and nonliving world Symbionts Fungi form symbiotic relationships with plants, algae, and animals All of these relationships have profound ecological effects

Mycorrhizae Mycorrhizae are enormously important in natural ecosystems and agriculture They increase plant productivity RESULTS RESULTS

Fungus-Animal Symbiosis Some fungi share their digestive services with animals These fungi help break down plant material in the guts of cows and other grazing mammals Many species of ants and termites use the digestive power of fungi by raising them in “farms”

Lichens Lichens are a symbiotic association of millions of photosynthetic microorganisms held in a mass of fungal hyphae The fungal component of a lichen is most often an ascomycete Algae or cyanobacteria occupy an inner layer below the lichen surface

A fruticose (shrub-like) lichen A foliose (leaf-like) lichen Crustose (crust-like) lichens

Ascocarp of fungus Soredia Fungal hyphae Algal layer Algal cell Fungal hyphae 10 µm

Pathogens About 30% of known fungal species are parasites, mostly on or in plants Animals are much less susceptible to parasitic fungi than are plants The general term for a fungal infection in animals is mycosis

Corn smut on corn Tar spot fungus of sycamore leaves Ergots on rye

Practical Uses of Fungi Humans eat many fungi and use others to make cheeses, alcoholic beverages, and bread Genetic research on fungi is leading to applications in biotechnology Antibiotics produced by fungi treat bacterial infections

Staphylococcus Penicillium Zone of inhibited growth

Animations and Videos Life Cycles of Zygomycetes, Ascomycetes and Basidomycetes The Ascomycetes Ascus Animation Basidium Animation The Basidiomycetes Conidia Animation Life Cycle of Cycle of a Zygomycetes Life Cycle of a Bread Mold

Animations and Videos Life Cycle of a Slime Mold Chapter Quiz Questions – 1 Chapter Quiz Questions - 2

You are presented with several single-celled organisms, including one thought to belong to the kingdom Fungi. What unique feature helps you identify the fungus? presence of mitochondria absence of chloroplasts presence of nuclei presence of chitinous cell walls Answer: d 43

You are presented with several single-celled organisms, including one thought to belong to the kingdom Fungi. What unique feature helps you identify the fungus? presence of mitochondria absence of chloroplasts presence of nuclei presence of chitinous cell walls 44

You are given a fungus to identify You are given a fungus to identify. It has a fruiting body that contains many structures with eight haploid spores lined up in a row. What kind of fungus is this? zygomycete chytrid deuteromycete ascomycete Answer: d 45

You are given a fungus to identify You are given a fungus to identify. It has a fruiting body that contains many structures with eight haploid spores lined up in a row. What kind of fungus is this? zygomycete chytrid deuteromycete ascomycete 46

Many fungi produce antibiotics, for example, penicillin, that are effective at stopping bacterial growth. Which do you think is the evolutionary advantage to the fungus of secreting antibacterial chemicals? defense: preventing bacteria from infecting the fungus defense: preventing bacteria from killing fungal spores symbiosis: attracting helpful bacteria competition: destroying bacteria that compete for their food predation: eventually consuming the bacteria Answer: d 47

Many fungi produce antibiotics, for example, penicillin, that are effective at stopping bacterial growth. Which do you think is the evolutionary advantage to the fungus of secreting antibacterial chemicals? defense: preventing bacteria from infecting the fungus defense: preventing bacteria from killing fungal spores symbiosis: attracting helpful bacteria competition: destroying bacteria that compete for their food predation: eventually consuming the bacteria 48

Which of the following phyla includes aquatic, flagellated fungi? Ascomycota Basidiomycota Chytridiomycota Zygomycota Answer: c 49

Which of the following phyla includes aquatic, flagellated fungi? Ascomycota Basidiomycota Chytridiomycota Zygomycota 50

Which of the following statements about mycorrhizae is false? They are important in natural systems and agriculture. Almost all vascular plants have them. Foresters inoculate pine seedlings with them to promote growth. They colonize soils by dispersing spores that form new mycelia. They are in a commensalistic relationship with plants. Answer: e

Which of the following statements about mycorrhizae is false? They are important in natural systems and agriculture. Almost all vascular plants have them. Foresters inoculate pine seedlings with them to promote growth. They colonize soils by dispersing spores that form new mycelia. They are in a commensalistic relationship with plants.

All of the following are lineages of fungi except a) chytrids. b) zygomycetes. c) glomeromycetes. d) ascomycetes. e) conidia. Answer: e

All of the following are lineages of fungi except a) chytrids. b) zygomycetes. c) glomeromycetes. d) ascomycetes. e) conidia.

Lichens are mutually beneficial relationships between fungi and plant roots. symbiotic associations between photosynthetic organisms and fungi. a type of plant pathogen. a type of marine eukaryote. single-celled, flagellated protist ancestors of fungi. Answer: b

Lichens are mutually beneficial relationships between fungi and plant roots. symbiotic associations between photosynthetic organisms and fungi. a type of plant pathogen. a type of marine eukaryote. single-celled, flagellated protist ancestors of fungi.

Chytrids are unique among fungi in that they have flagellated spores form mutualistic relationships with amphibians have led to the decline of sheep and cattle populations have chitinous cell walls Answer: a

Chytrids are unique among fungi in that they have flagellated spores form mutualistic relationships with amphibians have led to the decline of sheep and cattle populations have chitinous cell walls

The practical uses of fungi include all of the following except systemic mycoses. reducing high blood pressure. stopping maternal bleeding after childbirth. treating bacterial infections. fuel production. Answer: a

The practical uses of fungi include all of the following except systemic mycoses. reducing high blood pressure. stopping maternal bleeding after childbirth. treating bacterial infections. fuel production.