Kingdom Fungi (ch. 26) If at first you don’t like a fungus … Just wait a little, It will grow on you.  Mycology = study of fungi General Characteristics of Fungi Classification into Phyla / Divisions based on Sexual Reproductive Structures Effects on Humans – Diseases & Benefits * You should know all examples *

General Characteristics of Fungi Heterotrophic saprophytes (decomposers)  release / recycle inorganic nutrients Reproduce mostly asexually Haplontic life style – grow from haploid spores May also be parasitic, predatory, or form other symbioses

General Characteristics of Fungi Secrete digestive enzymes onto food  extracellular digestion  absorption of nutrients Digestive enzymes can digest tough substances, such as cellulose in wood Cell walls made of chitin, a polysaccharide Multicellular, except for yeasts (unicellular) Very efficient nutrient transport in hyphae  grow very fast! Most are poisonous  leave it to the experts to pick the fungus on your plate…

Important Symbioses Lichen = alga or cyanobacteria + fungus –> soil formation from rock Mycorrhyzae provide plant roots w/ inorganic nutrients, receive sugars

Fungal Structure - Cells Hypha = multinucleated, filamentous cell Fragmentation (asexual): new fungus grows from fragment ↓ Septate hyphae (septum = dividing wall) Coenocytic hyphae (no septa) Nuclei Nuclei Cell walls made of chitin

Fungal Structure - Body Mycelium = network of hyphae  body of fungus Fruiting body to disperse spores Hyphae Mycelium Mycelium of fungus on wood

“Fairy Rings” are mushrooms (fruiting bodies) that grow at the tips of an underground mycelium:

Generalized Fungal Life Cycle Haploid Spore Producing Structure: Mitosis (n  n) /Dikaryotic Sporulation n + n  2n SPEED: MAKE SPORES FAST! RECOMBINATION: GENETIC DIVERSITY 2n n n Sporulation Diploid Spore Producing Structure: Meiosis (2n  n)

Basidiomycota “Club Fungi” Basidiomycetes , Ernst Haeckel, 1904

*Basidium = Diploid Spore Producing Structure: Phylum Basidiomycota “Club” Fungi* Asexual reproduction: fragmentation of septate hyphae and asexual spores Sexual Reproduction Dikaryotic Stage KARYOGAMY n + n  2n PLASMOGAMY Secondary mycelium - mating type + mating type Primary mycelium Meiosis *Basidium = Diploid Spore Producing Structure: Meiosis (2n  n) The most familiar of all fungi are members of this large sub-division.  It includes some 25,000 described species, not only the mushrooms, toadstools, stinkhorns, puffballs, and shelf fungi but also two important plant pathogens: the rusts and smuts.  The Basidiomycota are distinguished from all other fungi by the production of basidiospores, which are borne outside a club-shaped, spore-producing structure called the basidium (plural, basidia).The basidia are produced by basidiocarps, which are the fruiting bodies of the so-called higher fungi, such as mushrooms and puffballs. Basidiocarps, like the ascocarps, are the large fruiting structures, which are the most visible stage of the fungus. A typical mushroom is a familiar example of a basidiocarp.                1) Life Cycle of Basidiomycota              The mycelium of the Basidiomycota is always septate and in most species passes through three distinct phases -primary, secondary, and tertiary- during the life cycle of the fungus.  When it germinates, a basidiospore produces the primary mycelium.  Initially the mycelium may be multinucleate, but septa soon form and the mycelium is divided into monokaryotic (uninucleate) cells. This septate mycelium grows by division of the terminal cell.  Branches do occur, and the mycelial mass can become very complex.  Commonly the secondary mycelium is produced by the fusion of primary mycelium from two different mating types (plasmogamy) [Figure 19].             The tertiary mycelium, which is also dikaryotic, arises directly from the secondary mycelium, and forms the basidiocarp. The spore forming basidia are produced by the terminal cell on millions of dikaryotic hyphae. In a typical mushroom, basidia are found on gills, under the cup (Figure 20A). Karyogamy occurs between the two haploid nuclei within a developing basidium. Then, the diploid nucleus undergoes meiosis to produce four haploid nuclei.  These nuclei then migrate into four small extensions at the apical end of the basidium, and are walled off to form the four basidiospores. Basidiospores n

Rusts & Smuts Affect Plant Crops Wheat stem rust - Puccinia graminis Smut fungus on corn

Plylum Ascomycota - “Sac” fungi (largest phylum) Cup fungi Includes Penicillium mold * Some species of the Ascomycota are asexual, meaning that they do not have a sexual cycle and thus do not form asci or ascospores. Previously placed in the Deuteromycota along with asexual species from other fungal taxa *Sac fungi include morels, truffles, brewer's yeast and baker's yeast, Dead Man's Fingers, and cup fungi. The fungal symbionts in the majority of lichens (loosely termed "ascolichens") such as Cladonia belong to the Ascomycota. There are many plant-pathogenic ascomycetes, including apple scab, rice blast, the ergot fungi, black knot, and the powdery mildews. Several species of ascomycetes are biological model organisms in laboratory research. Most famously Neurospora crassa, several species of yeasts, and Aspergillus species are used in many genetics and cell biology studies. Penicillium species on cheeses and those producing antibiotics for treating bacterial infectious diseases are examples of taxa that belong to the Ascomycota. Truffles

Penicillium mold, an ascomycete

Phylum Ascomycota n n + n  2n Conidiophore = Haploid Spore Producing Structure: Mitosis (n  n) - mating type Ascus = Diploid Spore Producing Structure: Meiosis (2n  n) + mating type Conidia, evolved from sporangia (zygomycota), are the main differentiating characteristic between asco and zygo n + n  2n n

Asexual Reproduction in Yeasts (unicellular ascomycote) Budding (MOTHER) CELL NEW YEAST CELL

Recent additions to Ascomycota… Athlete’s food & Ringworm

Zygomycota Ex.: black bread mold, Rhizopus stolonifer (asexual) The common example of a zygomycete is black bread mold (Rhizopus stolonifer), a member of the Mucorales. It spreads over the surface of bread and other food sources, sending hyphae inward to absorb nutrients. In its asexual phase it develops bulbous black sporangia at the tips of upright hyphae, each containing hundreds of haploid spores. As in most zygomycetes, asexual reproduction is the most common form of reproduction. Sexual reproduction in Rhizopus stolonifera, as in other zygomycetes, occurs when haploid hyphae of different mating types are in close proximity to each other. Growth of the gametangia commences after gametangia come in contact, and plasmogamy, or the fusion of the cytoplasm, occurs. Karyogamy, which is the fusion of the nuclei, follows closely after. The zygosporangia are then diploid. Zygosporangia are typically thick-walled, highly resilient to environmental hardships, and metabolically inert. When conditions improve, however, they germinate to produce a sporangium or vegetative hyphae.

Phylum Zygomycota - mating type + mating type Zygosporangium = Diploid Spore Producing Structure: Meiosis (2n  n) n 2n Sporangium = Haploid Spore Producing Structure: Mitosis (n  n)

(informal) Phylum Deuteromycota “Imperfect Fungi” because only observed to reproduce asexually May be moved to other phyla as research continues…

Predatory Fungus Nematode-Trapping Fungus Arthrobotrus , a deuteromycete, capturing a round worm (nematode) Predatory fungi have developed an astonishing array of trapping devices to capture nematodes as a food source. Species of the asexual fungus Arthrobotrys (Hyphomycetes, Deuteromycota) are probably the most common and certainly the best known predators of nematodes and have been the topic of many scientific and popular articles. The strategy for capture is fairly straightforward. Branching hyphae of the fungus ramify through soil, compost, dung, rotting wood, or wherever nematodes abound. Traps are initiated in response to a trap-inducing compound released by the nematodes themselves and are formed at intervals along the length of the hyphae. The trapping system is analogous to a fishing line with hooks at intervals.

Dimorphic Fungi 25 C 37 C Can exist as mold / hyphal / filamentous form (usually at room temperature) or yeast (body temperature)  several potential pathogens: Histoplasma capsulatum Found in bat and bird feces histoplasmosis; affects mainly lungs, can disseminate through body Candida albicans oral and genital infections

Benefits Medicines, including Penicillin, the first antibiotic, isolated from Penicillium fungus Food: edible mushrooms, moldy cheese , fermentation products (wine, beer), leavened bread (aerobic), etc. Biotechnology – yeasts used in research, including cloning of genes

OF ALCOHOL CONSUMPTION!!! Fungal Foods Yeast, sugar, aerobic respiration  CO2 makes bread rise Mold on blue cheese NOT AN ENDORSEMENT OF ALCOHOL CONSUMPTION!!! Alcoholic fermentation (anaerobic)