Kingdom Fungi The characteristics of fungi The evolution of the fungi Fungal classification Fungal life styles

Choanoflagellates Red algae Green algae Land plants Myxozoa Fungi Animals Figure: 29.2 Caption: This phylogeny shows the evolutionary relationships among the green plants, animals, fungi, and various groups of protists. Choanoflagellates are solitary or colonial protists found in fresh water and are introduced in Chapter 30. The ancestor of fungi is thought to have been a protist similar to the ancestor of animals

The Characteristics of Fungi Fungi are NOT plants Hyphae = tubular units of construction Mycelium = extensive, feeding web of hyphae Heterotrophic by absorption Reproduce by spores Ecologically pivotal roles

Hyphae Tubular Hard wall of chitin Crosswalls may form compartments (± cells) More than one nucleus 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

Hyphae grow from their tips Hyphal growth Hyphae grow from their tips This wall is rigid Only the tip wall is plastic and stretches

Mycelium = extensive, feeding web of hyphae 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 no one has seen one 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 are the ecologically active bodies of fungi

Heterotrophic by Absorption Fungi get carbon from organic sources Hyphal tips release enzymes Enzymatic breakdown of substrate Products diffuse back into hyphae Enzymatic breakdown Nucleus hangs back and “directs” Products Enzymes Product diffuses back into hypha and is used

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

fruiting bodies both consist of hyphae mycelium

Multicellular and Unicellular fungi Figure 29.3 138 µm 3.73 µm

Simple Fungi Fig 31.5 Chytridium growing on spores 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 Fig 31.5 Chytridium growing on spores

Molds Fig 31.6 Rhizopus on strawberries Most of the 600 zygomycote, or zygote fungi, are terrestrial, living in soil or on decaying plant and animal material. Asexual reproduction in sporangia One zygomycote group form mycorrhizas, mutualistic associations with the roots of plants. Fig 31.6 Rhizopus on strawberries

Molds 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

Club Fungi 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

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

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

Fungal Ecology ECOLOGICAL ROLES: Saprobes Parasites Mutualists 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

Fungal Ecology Saprobes Decomposers Mostly of plants, some animals 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

Fig 31.6 Rhizopus on strawberries Most of the 600 zygomycote, or zygote fungi, are terrestrial, living in soil or on decaying plant and animal material. Asexual reproduction in sporangia One zygomycote group form mycorrhizas, mutualistic associations with the roots of plants. Fig 31.6 Rhizopus on strawberries

Fungi are absorptive heterotrophs that secrete digestive enzymes and are major decomposers of dead organic material.

Fungal Ecology Parasites Harm host Mostly on plants, some animals 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

Rusts & Smuts A rust growing on a currant leaf 0.5 cm 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.

Parasitic fungi cause major damage to crops such as wheat, corn, and barley. Many have evolved resistance to fungicides.

Fungal Ecology Mutualists Mycorrhizas Lichens 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

Mycorrhizas “Fungus roots” Mutualism between: Several kinds Fungus (nutrient & water uptake for plant) Plant (carbohydrate for fungus) Several kinds 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

Figure 29.9a Ectomycorrhizal fungi (EMF) Root cells EMF Figure: 29.9a Caption: (a) Ectomycorrhizal fungi (EMF) form a dense network around the roots of plants. The combination of root and fungus is called a mycorrhiza. The drawing shows how the interaction works in EMF. Note that their hyphae penetrate the intercellular spaces of the root, but do not enter the cells themselves.  EMF

Mutualism: Relationships between fungi and hosts that are mutually beneficial Increasing the diversity of mycorrhizae in a given habitat increases plant species richness and productivity

Lichens “Mutualism” between Form a thallus Fungus – protection against drying Alga or cyanobacterium – provides food Form a thallus Foliose Fruticose Crustose 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 Asci produced by fungus Asexual reproduction occurs when “mini-lichens” are produced. Fungal layer Algal layer Figure: 29.11a Caption: (a) In a lichen, green algae or cyanobacteria are enmeshed in a dense network of fungal hyphae. In this example, the fungal participant is an ascomycete. Fungal layer Substrate

Lichen internal structure 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.

Lichens as biomonitors Some species more sensitive Which species are present can indicate air quality Analysis for sulfur and heavy metals in resistant species shows levels relative to levels in the environment