Chapter 31

Chapter 31 - Fungi

IV. Kingdom Fungus

A. Estimated 1.5 million species B. Greek, mycos, fungi (mycelium, mycorrhizae, etc…) C. Some are single-celled (in general known as yeast), while most are complex multicellular D. Fungi are heterotrophs that absorb food after digesting with enzymes they secrete outside their body called exoenzymes

hyphae

Fig. 17.16

Chapter 31 - Fungi

IV. Kingdom Fungus E. Types 1. Saprophytes (saprobes, decomposers) - Break down and absorb nutrients from non-living organic material like a fallen log, dead animals and organismal waste (feces, etc…)

Fig. 17.16

Chapter 31 - Fungi

IV. Kingdom Fungus E. Types 2. Parasitic / Pathogens - Take nutrients from living cells, some pathogenic – 80% of plant diseases caused by fungus.

“Athletes Foot”

Blithe

Only 50 out of the known 100,000 fungal species are parasites of animals and these do relatively little damage.

Chapter 31 - Fungi

IV. Kingdom Fungus E. Types 2. Parasitic / Pathogens - Of the 100,000 known fungal species, 30% are parasites mostly of plants:

- Between 10% and 50% of world fruit harvest lost each year to fungus

Chapter 31 - Fungi

IV. Kingdom Fungus E. Types 3. Mutualistic symbionts - mycorrhizae

mycorrhizael hyphae

Fig. 17.16

Chapter 31 - Fungi

IV. Kingdom Fungus F. Body Structure

1. Multicellular fungus - Hyphae - Network of tiny filaments making up body of fungus - Cell walls are made of… Chitin = polysaccharide of modified glucose also found in exoskeletons of insects and crustaceans (arthropods) - Mycelium (plural, mycelia) – entire interwoven mass of hyphae - High surface area to volume ratio, efficient feeding - 1ml of soil may contain 1km of hyphae - Like plants, hyphae need to GROW through environment

Fig. 17.16

Chapter 31 - Fungi

IV. Kingdom Fungus F. Body Structure

1. Multicellular fungus - Structure of Hyphae a. Septate hyphae - Most fungi have hyphae divided into cells by septa (crosswalls) with large pores for sharing material b. Coencytic hyphae – continuous cytoplasm with many, many nuclei due to repeated mitosis without cytokinesis similar to slime molds.

Fig. 17.16

Chapter 31 - Fungi

IV. Kingdom Fungus F. Body Structure 1. Multicellular fungus - Structure of Hyphae c. There are hyphae adapted for trapping and killing d. Haustoria – specialized hyphae that can penetrate host cells.

Fig. 17.16

Chapter 31 - Fungi

IV. Kingdom Fungus G. Life cycle of fungi 1. Produce spores either sexually or asexually - Carried by wind or water - We see this when we leave food out or in fridge too long…spores are everywhere in the air….

Puffball mushroon exploding releasing trillions of spores

Chapter 31 - Fungi

IV. Kingdom Fungus G. Life cycle of fungi 2. General life cycle of fungus: - Many, but not all reproduce both sexually and asexually. Some do one or the other. - nuclei of hyphae and spores are haploid.

Chapter 31 - Fungi

IV. Kingdom Fungus G. Life cycle of fungi 2. General life cycle of fungus: Sexual reproduction - Begins when two distinct mycelia of different mating types secrete pheromones that bind to receptors on each others surfaces. - Hyphae then move toward each other (source of pheromone) and fuse = plasmogamy.

Chapter 31 - Fungi

IV. Kingdom Fungus G. Life cycle of fungi 2. General life cycle of fungus: Sexual reproduction - Haploid nuclei do not fuse right away in many fungi resulting in mycelia with genetically different nuclei = heterokaryon (“different nucleus”). - Dikaryotic mycelia – if heteronuclei pair off two to a cell.

Chapter 31 - Fungi

IV. Kingdom Fungus G. Life cycle of fungi 2. General life cycle of fungus: Sexual reproduction - Hours, days or years may pass until karyogamy (fusion of nuclei) occurs resulting in only diploid stage. - Meiosis follows karygomy restoring haploid mycelium and more spores will be made by mitosis.

Chapter 31 - Fungi

IV. Kingdom Fungus G. Life cycle of fungi 2. General life cycle of fungus: ASexual reproduction - Clones made by mitotic cell division of specialized cells in mycelia to form spores…which undergo mitosis to make new mycelia.

Chapter 31 - Fungi

IV. Kingdom Fungus G. Life cycle of fungi 2. General life cycle of fungus: Molds - Any multicellular fungus that can reproduce rapidly and asexually. It is a general term. Many of these fungi can reproduce sexually, but mold refers only to the asexual stage. Deuteromycetes (aka imperfect fungi) - Molds or yeasts with no sexual stage.

Yeast - Reproduce predominantly asexually not by using spores, but by budding, a type of simple form of cell division. Sometimes they reproduce sexually.

Chapter 31 - Fungi

IV. Kingdom Fungus H. Fungi Evolved from a single-celled flagellated protists The five major phyla of fungi:

Chapter 31 - Fungi

IV. Kingdom Fungus H. Fungi Evolved from a single-celled flagellated protists 1. Chytridiomycota (Chytrids) - Found in lakes and soil, some saprobes others parasitic - First to diverge - Unique from other fungi in that their spores have flagella called zoospores. As you would expect if common ancestor were flagellated protist…

Chapter 31 - Fungi

IV. Kingdom Fungus H. Fungi Evolved from a single-celled flagellated protists 2. Zygomycetes - 1000 known species - Fast growing molds that rot produce like fruit and bread… - Other live as parasites or commensal on animals - Characterized by presence of sexually produced heterokaryotic zygosporangium

Chapter 31 - Fungi

IV. Kingdom Fungus H. Fungi Evolved from a single-celled flagellated protists 2. Zygomycetes Life cycle of black bread mold

Goes sexual when environmental condition deteriorate like food scarce forming zygosporangia.

zygosporangia Resistant to freezing and drying and are metabolically inactive.

Chapter 31 - Fungi

IV. Kingdom Fungus H. Fungi Evolved from a single-celled flagellated protists 3. Glomeromycetes - 160 species known - All form endomycorrhizae called arbuscular mycorrhizae Arbuscule

Chapter 31 - Fungi

IV. Kingdom Fungus H. Fungi Evolved from a single-celled flagellated protists 4. Ascomycetes - 32,000 species - Production of sexual spores in saclike asci - Therefore commonly called sac fungi - Vary from unicellular yeast including bread/beer/wine making yeast (Saccharomycetes cerevisiae) to cup fungi and morels

- Consist of some of most deadliest plant pathogens making them relevant to agriculture - More than 40% are lichens – mutualistic relationship between fungi and unicellular chlorophytes (green algae) or with cyanobacteria.

- Others form mycohorrhizae

Lichen growing on a tree:

Chapter 31 - Fungi

IV. Kingdom Fungus H. Fungi Evolved from a single-celled flagellated protists 4. Ascomycetes - lichen:

The fungus can reproduce sexually as will be discussed via the ascocarp, while the algae will reproduce asexually.

The fungus can also reproduce asexually if fragments called Soridia break off becoming a new lichen after many round of mitotic division.

Chapter 31 - Fungi

IV. Kingdom Fungus H. Fungi Evolved from a single-celled flagellated protists 4. Ascomycetes - Neurospora crassa i. Best studied ascomycete ii. A common bread mold iii. Life cycle:

Conidia = asexual spores Ascospores are within asci, which are within the ascocarp

Chapter 31 - Fungi

IV. Kingdom Fungus H. Fungi Evolved from a single-celled flagellated protists 5. Basidiomycetes - Club fungi - 30,000 species - Named after the basidium (little pedestal) – a cell in which a transient diploid stage occurs. - Important decomposers (best fungi at breaking down lignin), some form mycorrhizae, others are plant parasites - Toad stools

Chapter 31 - Fungi

IV. Kingdom Fungus H. Fungi Evolved from a single-celled flagellated protists 5. Basidiomycetes - Life Cycle

Chapter 31 - Fungi

IV. Kingdom Fungus

A. Fungus

hyphae