Fungi April 4th Mutualistic Relationship with Animals • Arthropods depend on the fungus for protection from predators and pathogens, while the fungus obtains nutrients and a way to disseminate spores into new environments. • Leaf cutting ants farm fungi as source of nutrients. Fungivores • Animal dispersal is important for some fungi because an animal may carry spores considerable distances from the source. • Fungal spores are rarely completely degraded in the gastrointestinal tract of an animal, and many are able to germinate when they are passed in the feces. Animal and Human Parasites and Pathogens • A mycosis is a fungal disease that results from infection and direct damage. Fungi attack animals directly by colonizing and destroying tissues. • Mycotoxicosis is the poisoning of humans (and other animals) by foods contaminated by fungal toxins (mycotoxins). • Mycetismus describes the ingestion of preformed toxins in poisonous mushrooms. Plant Paracites and Pathogens • Many plant pathogens are fungi that cause tissue decay and eventual death of the host. • In addition to destroying plant tissue directly, some plant pathogens spoil crops by producing potent toxins. Classification of Fungi • Fungi are classified according to their methods of reproduction and their basic structure. Oomycota – Protist-like Fungi • Oomycetes commonly form a white fuzz on aquarium fish or organic matter sitting in water. • They are commonly known as “water molds,” few of them can grow on land under damp, humid conditions. • They do cause a number of serious diseases among crop, plants, including potato blight. Oomycota – Protist-like Fungi • Oomecetes have thin cell wall made of cellulose that absorb nutrients through. • They are the only fungi that produce motile spores. These spores swim through water and raindrops to new sources of food. • Oomycetes lack cross walls; the hyphae are multinucleate. Oomycota – Protist-like Fungi • In asexual reproduction, portion of the hyphae develop into sporangia and create flagellated spores. • In Sexual reproduction, hyphae form antheridium (producing male gametes), and oogonium (producing female gametes). Zygomycota – Common Molds • Zygomycetes are terrestrial organism. • The hyphae of zygomycetes lack cross walls although there are cross walls present that isolate the reproductive structures from rest of the hypha. • During sexual reproduction, they form a thick-walled zygote known as zygospore. Zygomycota – Common Molds • During asexual reproduction, sporangia produce spores. • A single sporangium may contain as many as 40,000 spores that gets carried by the wind. • Common example of this phylum is black bread mold Rhizopus Stolonifer. Ascomycota – Sac Fungi • This phylum is the largest phylum of the kingdom Fungi (30,000 species). • The nuclei in the hyphae of ascomycetes are separated by cross walls so that individual cells do exist within the organism. • In the cell wall, holes exist so cytoplasm and the nuclei can move. Ascomycota – Sac Fungi • Ascomycetes reproduce asexually by producing extra small spores called conidia that are formed at the tip of specialized hyphae called conidiophores. • Sexual reproduction involves the formation of an ascus (a tiny sac)that contain different mating type (+ and -). • When the two type meets, gametangia is formed to create haploid nuclei. Basidiomycota – Club Fungi • Most of the organism that we call mushrooms belong to this phylum. • The spore producing structure is called a basidium that can be found in the cap. Basidiomycota – Club Fungi • Basidiospore germinates to produce haploid primary mycelia. • Other haploid primary mycelia of different mating type may fuse into secondary mycelia, and grow in the soil for years reaching enormous size. Deuteromycota – Imperfect Fungi • This phylum contains fungi that their sexual reproduction has never been observed. • They lack of sexual reproduction. • Majority of the deuteromycetes closely resemble ascomycetes. Rest are similar to basidiomycetes. Deuteromycota – Imperfect Fungi • Example of ascomycetes is Penicillium, which are fungi that are used to antibiotic penicillin. • Penicillium reproduces asexually by means of conidia. • Deuteromycota is phylum that is most infamous; can cause ringworm, athletes food, and other skin infection.
