Warm up What do you think is the largest living organism on Earth? Armillaria ostoyae (honey mushroom) at least 2,400 years old How large do you think it is? covers 2,200 acres (3.5 miles across, 3 feet deep) about 1,665 football fields

Kingdom Fungi The characteristics of fungi Fungal life styles This smaller-sized file version lacks the photographic reviews of fungal diversity and only has the “main” slides All photographsin this presentation © Pearson Education or Fred M. Rhoades

The Characteristics of Fungi Fungi are NOT plants Most multicellar, some unicellular (yeast) Hyphae = tubular units of construction, made of chitin Heterotrophic by absorption Reproduce by spores Ecologically pivotal roles

Hyphae Slender tubes Hard wall of chitin Crosswalls may form compartments (± cells) Multinucleate Grow at tips Chitin is the same material used by Arthropods (Insects, crabs, etc.) in their exoskeletonsa Nuclei of fungi are hard to see without stains

Heterotrophic by Absorption Fungi get carbon from organic sources Hyphal tips release enzymes Enzymatic breakdown of substrate Products diffuse back into hyphae Enzymatic breakdown Most enzyme release (and absorption) at tips Proteins and other materials synthesized by the entire mycelium are channeled by cytoplasmic streaming to the tips of the extending hyphae. Nucleus hangs back and “directs” Products Enzymes Product diffuses back into hypha and is used

Fig 31.1 fruiting bodies both are composed of hyphae mycelium

Modifications of hyphae Fig 30.2 (don’t worry about the terms)

Hyphal growth Hyphae grow from their tips Mycelium = extensive, feeding web of hyphae Mycelia are the ecologically active bodies of fungi This wall is rigid Only the tip wall is plastic and stretches

Reproduce by spores Spores are reproductive cells Formed: Sexual Asexual Formed: Directly on hyphae Inside sporangia Fruiting bodies Fungi reproduce by releasing spores that are produced either sexually or asexually. The output of spores from one reproductive structure is enormous, with the number reaching into the trillions. Dispersed widely by wind or water, spores germinate to produce mycelia if they land in a moist place where there is food. Penicillium hyphae Pilobolus sporangia Amanita fruiting body

Hyphal growth from spore germinating spore Fungal mycelia can be huge, but they usually escape notice because they are subterranean. One giant individual of Armillaria ostoyae in Oregon is 3.4 miles in diameter and covers 2,200 acres of forest, It is at least 2,400 years old, and weighs hundreds of tons. (Actually noone has seen this of this extent – but cultures have been taken from soil over that area and all isolates have been found to be the same individual) Ten cubic centimeters of rich organic soil may have fungal hyphae with a surface area of over 300 cm2 mycelium Mycelia have a huge surface area (think honey mushroom)

Fungal Ecology Saprobes Parasites Mutualists Decomposers Mostly of plants, some animals Parasites Harm host Mostly on plants, some animals Mutualists Lichens Mycorrhizas Others Saprobic fungi absorb nutrients from nonliving organisms. Parasitic fungi absorb nutrients from the cells of living hosts. Some parasitic fungi, including some that infect humans and plants, are pathogenic. Mutualistic fungi also absorb nutrients from a host organism, but they reciprocate with functions that benefit their partner in some way

Yeasts Lichens Molds Mycorrhizas A rust growing on a currant leaf Rusts are Basidiomycote plant parasites with, often, very complex life cycles that alternate between two different plant hosts. They can produce up to 5 different types of spores and cause considerable damage, particularly to economically important plant hosts that are non-natives. A rust growing on a currant leaf 0.5 cm

Yeasts Single celled fungi Adapted to liquids Plant saps Water films Moist animal tissues Bread and wine yeast, the budding yeast, Saccharomyces Easily cultured. For a time, this was the most important organism for studying the molecular genetics of eukaryotes Thus, Saccharomyces is arguably the most important organism known to humans Candida causes diseases of humans, usually experiencing chemical imbalance or immune problems Candida Saccharomyces

Lichens “Mutualism” between Fungus – structure Alga or cyanobacterium – provides food Thallus is a plant-like body that doesn’t have roots, stems or leaves Thallus doesn’t look like either partner Dual nature of thalli was not fully understood until early 1900’s Fungus gives the name to the lichen (by agreement) Fungus usually, but not always, an Ascomycote (in 8+ independent orders) Algae green. If bluegreen bacteria present, lichens fix nitrogen (turn atmospheric nitrogen into amino acid nitrogen in proteins) Fig 31.16

Lichen internal structure Fig 31.17 The nature of lichen symbiosis is may also be described as mutual exploitation instead of mutual benefit. Lichens live in environments where neither fungi nor algae could live alone. While the fungi do not not grow alone in the wild, some (but not all) lichen algae occur as free-living organisms. If cultured separately, the fungi do not produce lichen compounds and the algae do not “leak” carbohydrate from their cells. In some lichens, the fungus invades algal cells with haustoria and kills some of them, but not as fast as the algae replenish its numbers by reproduction. Lobaria oregana prefers old-growth conifer canopies in forests with clean air. Lobaria

Schizosaccharomyces octospora – fermenter of Palm Wine This yeast is isolated from palm wine (fermented sap of the oil palm in West Africa) Note that it is forming 8-spored asci (“octospora”) – an indication that it is an Ascomycote 10 μm

Molds Rapid growth Asexual spores Many human importances Food spoilage Food products Antibiotics, etc. A mold is a rapidly growing, asexually reproducing fungus. The mycelia of these fungi grow as saprobes or parasites on a variety of substrates. Also used in foods (Blue cheese, Tempeh) and in industrial production of drugs Early in life, a mold, a term that applies properly only to the asexual stage, produces asexual spores. Later, the same fungus may reproduce sexually, producing zygosporangia, ascocarps, or basidiocarps Some molds go through a “fake sex” process Noble Rot - Botrytis Fig 31.21 Antibiotic activity

Mycorrhizas “Fungus roots” Mutualism between: Several kinds Fungus (nutrient & water uptake for plant) Plant (carbohydrate for fungus) Several kinds Zygomycota – hyphae invade root cells Ascomycota & Basidiomycota – hyphae invade root but don’t penetrate cells Extremely important ecological role of fungi! Half of the mushroom-forming fungi (basidiomycota) form mycorrhizas with trees Some people think that the spongy tissue in roots evolved as a place where fungi could invade to form early links with plants that helped them survive the harsh life on early earth

“Ecto”mycorrhizas Russula mushroom mycorrhizas on Western Hemlock root Mycorrhiza cross sections 4 of the regions where mycorrhizas are found are circled. These are “ecto” because the hyphae remain outside the root cells (though they extend inside the root) Fungal hyphae around root and between cells

Mushroom Life Cycle Hyphal fusion of haploid mycelia mycelium and fruiting body are dikaryotic haploid mycelium Mushroom Life Cycle N 2N N+N Meiosis Nuclear fusion in basidium young basidia - the only diploid cells Fig 31.12