Fungi

Characteristics of Fungus

Eukaryotic

Nonphotosynthetic

Multicellular

Heterotrophic

Saprophytic (most)

Store energy in the form of glycogen.

Molds – mass of tangled filaments of cells, bread mold.

Yeasts – unicellular fungus whose colonies resemble those

of bacteria; make bread rise by producing CO2.

Characteristics of Fungus

Hyphae – filaments of fungus;

Mycology – the study of fungi.

Characteristics of Fungus -some hyphae have separating walls called septa. -The hyphae of other fungi do NOT have septa and are called coenocytic.

-Hyphae have cell walls composed of chitin, a complex polysaccharide that is found in insects.

Characteristics of Fungus

Mycelium - a mat of hyphae visible to the unaided eye.

Dimorphism - the ability to change into different forms, depending on the environment. Histoplasma capsulatum grows as mycelium on the ground, but in the lungs of humans it forms unicellularly.

Asexual Reproduction in Fungi

Asexually, fungi produce thousands of genetically identical haploid spores, usually on modified cells of the hyphae.

Different fungi produce different types of spores.

Sporangiophores – specialized hyphae that look like upright stalks.

Sporangium – an enclosed sac on top of the sporangiophore.

Sporangiospores – haploid spores found inside the sporangium. Rhizopus (bread mold) forms sporangiospores.

Conidia – fungal spores that are formed without the protection of an enclosing sac.

Conidiophore – stalklike structure - conidia form on the top. Penicillium, which produces penicillin and cheese, reproduces asexually by means of conidia.

More Fungus Asexual reproduction

Fragmentation - a septate hypha dries and shatters, releasing individual cells that act as spores. Trichophyton species or Epidermophyton species, the fungi that cause athlete’s foot reproduce this way.

Budding – an asexual process in which part of a yeast cell pinches itself off to produce a small off spring cell.

Sexual Reproduction Fungi are neither male nor female. They occur in mating types that are sometimes referred to as “minus” and “plus.” When two different mating types of the same species encounter one another, the hypha fuse together and produce a new fungus.

The ability to reproduce sexually and asexually provides an adaptive advantage. When the environment is favorable, rapid asexual reproduction ensures an increased spread of the species.

During environmental stress, sexual reproduction ensures genetic recombination, increasing the likelihood that offspring are better adapted to the new environment.

Evolution

1st fungi were probably unicellular organisms that clung together after mitosis to form a long filament of cells.

Colonized dry land at about the same time as early plants.

Arose from prokaryotes, possibly by endosymbiosis.

All modern phyla of fungi evolved by about 300 million years ago.

Classification of Fungi

Phylum Zygomycota

Terrestrial, found in soil.

Hyphae are coenocytic.

Reproduce sexually and asexually.

Rhizoids – a rootlike structure that anchors fungal hyphae to a solid substance. They release digestive enzymes that break down organic compounds to release nutrients.

Stolon – hyphae growing on the surface of organic material.

Rhizopus stolonifer - common bread fungus which belongs to Zygomycota, produces rhizoids and stolon across bread.

Gametangium - a sexual reproductive structure that contains a nucleus of a mating type(+ or -). When the gametangia fuse from different mating types, the nuclei mix and fuse in pairs, each pair containing a nucleus from each mating type.

Zygosporangium – fused gametangia; forms a thick wall and becomes dormant. Germination depends on environmental conditions.

Meiosis

Classification of Fungi

Phylum Basidiomycota (club fungi)

Basidiocarp - spore-bearing structure of basidiomycetes which grows above ground - consists of stem called a stalk and flattened structure known as a cap.

Gills - one of the radiating rows on the underside of the cap.

Basidia - small clublike reproductive structures; - used for sexual reproduction forms on the gills

- Dikaryotic – cells containing 2 nuclei; when the two nuclei fuse together they form a zygote.

Basidiospores – formed after the zygote undergoes meiosis to form four haploid nuclei. -released into the air when fully developed. -germinate to produce haploid mycelia that grow underground; when mating types encounter one another, their hyphae fuse and form a basidiocarp.

Classification of Fungi

Phylum Ascomycota (Sac Fungi)

Spores are contained in sacs.

Parasitic

Found in salt water, freshwater & land.

Saccharomyces cerevisiae - brewer’s & baker’s yeast

Sexual Reproduction.

Ascogonium – female gametangium (n) formed from hyphae.

Antheridium – male gametangium (haploid) formed from hyphae.

Ascocarp – a visible cuplike structure formed when dikaryotic hyphae grow out of the ascogonium and intertwine with the monokaryotic hyphae of the original fungi (parents).

Ascocarp

Monokaryotic – cells that contain one nucleus.

Asci – sacs found with in the ascocarp that produce ascospores.

Ascospores – formed within the asci when the haploid nuclei fuse. The zygotes undergo meiosis once and divide again by mitosis to form eight haploid nuclei. The nuclei form walls and become ascospores.

Asci

Mycorrhizae & Lichens Mycorrhiza – mutualism between a fungus and plant roots.

- 90% of all plants contain mycorrhiza. - Provides nutrients(phosphates) to the plant & fungi receives sugars from plant.

Lichens - symbiotic relationships between a fungus and a photosynthesizer (usually a cyanobacteria or green alga).

Most are ascomycetes.

Photosynthesizer producers sugars for fungus.

Fungus provides moisture, shelter and anchors photosynthesizer.

Fungus produces acids that decompose rocks into soils, thus providing minerals to lichen.

Classification of Lichens

Identified according to their distribution and structure.

Crustose – lichens that grow as a layer on the surface of rocks and trees.

Classification of Lichens

Identified according to their distribution and structure.

Fruticose - shrublike lichens; grow up to 1.5 m.

Classification of Lichens

Identified according to their distribution and structure.

Foliose - lichens that live on flat surfaces, where they form matlike growths with tangled bodies.

Fungi & Humans

Fungal Skin Infections

Athlete’s Foot (Trichophyton species or Epidermophyton species) Symptoms: fluid-filled blisters, scaly skin, itching

Route of Transmission: contact with skin lesions or contaminated floors.

Fungi and Humans

Ringworm (Microsporum, Trichophyton species) Symptoms: ring-shaped skin lesions.

Route of Transmission: contact with skin lesions or contaminated floors, or objects.

Fungi and Humans

Yeast Infection (Candida albicans) Symptoms: burning sensation, itching, discharge. Route of Transmission: contact with fecal material, diabetes; antibiotic treatments increase susceptibility. Yeast infections are found in both males and females.

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Histoplamosis (Histoplasma capsulatum) Symptoms: fever, chills, headache, body aches, chest pains, nonproductive cough. Route of Transmission: inhalation of airborne conidia.

Other Fungal Illnesses

Toxic Mushrooms

“Death Angel” (Amanita virosa) – can destroy the human liver in one week.

Aflatoxins – poisons produced by some species of Aspergillus.

- Cause liver cancer. - Found in peanuts and grains such as corn

and sorghum.

Fungi In Industry

Penicillium – produces penicillin.

Cephalosporium – produces cephalosporin antibiotics.

Rhizopus – used to make cortisone.

Saccharomyces cervisiae (yeast) – used to produce vaccines for hepatitis B.

Rhizopus

Fungi & Food Industries

Penicillium species – cheeses: blue, brie, Camembert, Gorgonzola, Limburger, Roquefort.

Saccharomyces carlsbergensis, Saccharomyces cerevisiae – Beer, wine.

Camembert

Fungi & Food Industries

Aspergillus oryzae, Rhizopus species, Mucor species – Soy products: miso (Japanese), soy sauce, tempeh (Indonesian), tofu (Japanese).

Ashbya gossypii – produces vitamin B2, a nutritional supplement.

Of the more than 100,000 species of fungi known, only about 100 are pathogenic to humans and other animals. However, thousands of fungi are pathogenic to plants. Almost every economically important plant is attacked by one or more fungal species.

Truffles

Morels