Chapter 22 Fungi PDF

Witches Cauldron Sarcosoma globosum Roy V. Rea Fungi 22 Chapter Word of the Day “Karyogamy” Lecture Outline Defining Fungi Fungal roles in the environment Fungal reproduction and taxonomy Defining fungal groups A word on lichens Overview: Mighty Mu...

Witches Cauldron Sarcosoma globosum Roy V. Rea Fungi 22 Chapter Word of the Day “Karyogamy” Lecture Outline Defining Fungi Fungal roles in the environment Fungal reproduction and taxonomy Defining fungal groups A word on lichens Overview: Mighty Mushrooms Fungi are diverse and widespread Field Camp Mycology Module, Mudzenchoot Park, BC, R.V. Rea Fungi are heterotrophs that feed by absorption Fungi break down organic material and recycle important nutrients They serve as food, root associations with plants, can be symbionts, but can also attack crops, and be Roy V. Rea pathogenic. Many are saprotrophs that decompose the non-living. Many are fine edibles… Fig. 31-1 Boletus sp. Sebastapol, California Link Van Cleave Nutrition and Ecology Fungi are heterotrophs and absorb nutrients from outside of their body Fungi use digestive exoenzymes to break down a large variety of complex molecules into smaller organic compounds The versatility of these enzymes contributes to fungi’s ecological success R.V. Rea R.V. Rea Body Structure Fungi exhibit diverse lifestyles: – Decomposers (e.g., chaga) Ricinet.ca – Parasites (e.g., ringworm) John Prince Research Forest, February 16, 2017 – Mutualists (e.g., mycorrhizae) R. Rea Scienceline.org Pine beetle spread blue stain fungus Fungal Body Structure can desiccate easily!! Common body structures are multicellular filaments (hyphae) and single cells (yeasts) Some species grow as either filaments or yeasts; others grow as both See Fig. 25.13 Candida sp. – a yeast Fungal Morphology The morphology of multicellular fungi enhances their ability to absorb nutrients Fungi consist of mycelia, networks of branched hyphae adapted for absorption Roy V. Rea A Hawaiian basidiomycete, Lulumahu trail, Oahu Specialized Hyphae in Mycorrhizal Fungi Some, but not all fungi have cell walls made of chitin, glucose polymers, mannoproteins (& waxes) Some unique fungi have specialized hyphae called haustoria that allow them to penetrate the tissues of their host See Fig. 22.12a. Arthrobotrys lassoing and constricting a nematode Mycorrhizae benefit both fungi and plants Arbuscular mycorrhizal fungi extend hyphae through the cell walls of root cells and invaginate the root cell membrane Fig. 22.10 Ectomycorrhizal fungi form sheaths of hyphae over a root and also grow into the extracellular spaces of the plant root cortex (but not through the cell walls!!) Fungi produce spores through sexual or asexual life cycles Fungi propagate themselves by producing vast numbers of spores, either sexually or asexually Fungi can produce spores from sexual and asexual life cycles Fig. 22.4 Roy V. Rea Sexual Reproduction (see Fig. 22.7) Fungal nuclei are normally haploid, with the exception of transient diploid stages formed during the sexual life cycles Sexual reproduction requires the fusion of hyphae from different mating types (+ or -) Roy V. Rea Fungi use sexual signaling molecules called pheromones to communicate their mating type Sexual Reproduction (see Fig. 22.7) Plasmogamy is the union of two parent mycelia In most fungi, the haploid nuclei from each parent do not fuse right away; they coexist in the mycelium, called a heterokaryon In some fungi, the haploid nuclei pair off two to a cell; such a mycelium is said to be dikaryotic Roy V. Rea Sexual Reproduction (see Fig. 22.7) Hours, days, or even centuries may pass before the occurrence of karyogamy, nuclear fusion During karyogamy, the haploid nuclei fuse, producing diploid cells The diploid phase is short-lived (can take years but not centuries) and undergoes meiosis, producing haploid spores Fungal fruiting bodies of Fly agaric (Amanita muscaria) pre- and post spore release Roy V. Rea  Sexual Reproduction (see Fig. 22.7) The life cycle of black bread mould (Rhizopus stolonifer) is fairly typical of the phylum Zygomycota Edtechlens Roy V. Rea Asexual Reproduction In addition to sexual reproduction, many fungi can reproduce asexually Moulds produce haploid spores by mitosis and form visible mycelia Figure 22.19 One species of black mould One species of white mould Asexual Reproduction Other fungi that can reproduce asexually are yeasts, which inhabit moist environments Instead of producing spores, yeasts reproduce asexually by simple cell division and the pinching of “bud cells” from a parent cell James Heilman, MD Fig. 22.13 Yeast cells budding Candidiasis from Candida albicans Deuteromycetes Many moulds and yeasts have no known sexual stage (assumed to reproduced asexually only) Mycologists have traditionally called these deuteromycetes, or imperfect fungi These do not fit neatly into any fungal phylum Tremella sp., a fungal parasite that produces amorphous yeast states, but occasionally has orange fruiting bodies (Basidiocarps), so not a Deuteromycete. Roy V. Rea Fungal Phylogeny DNA evidence suggests that fungi are most closely related to unicellular nucleariids while animals are most closely related Nuclearia thermophila to unicellular choanoflagellates This suggests that fungi and animals evolved from a common flagellated unicellular ancestor and multicellularity arose separately in the two groups (did she look like this?) The oldest undisputed fossils of fungi are only ~ 460 my old Iñaki Ruiz-Trillo  Fungi were among the earliest colonizers of land (~760 mya) and probably formed mutualistic relationships with early plants Animals and fungi shared a common ancestor about.85-1.5 bya Rea family, collecting Hedgehogs Chytrids Chytrids (phylum Chytridiomycota) are decomposers, parasites, & mutualists found in freshwater and terrestrial habitats Molecular evidence supports the hypothesis that chytrids diverged early in fungal evolution Chytrids are unique among fungi in having flagellated spores, called zoospores Fig. 22.6  File:Batrachochytrium dendrobatidis.jpg Fig. 31-12 Batrachochytrium sp. Zoospore on arthropod Zoospore on alga Not all Fungi are Toadstools! File:Synchytridium endobioticum.jpg Flagellum 4 µm Synchytridium sp. (potato fungus) USDA Zygomycetes The zygomycetes (phylum Zygomycota) exhibit great diversity of life histories They include fast-growing (e.g., bread) molds, parasites, and commensal symbionts The zygomycetes are named for their sexually produced zygospores (remember the life cycle of the bread mould) Zygospores, which are resistant to freezing and drying, can survive unfavorable conditions Zygomycetes Some Zygomycetes, such as Pilobolus, can actually “aim” their sporangia toward conditions associated with good food sources Fig. 22.9 https://www.youtube.com/watch?v=iOanDmeVn3c Glomeromycetes The glomeromycetes (phylum Glomeromycota) were once considered Zygomycetes, but are a separate clade Glomeromycetes form arbuscular mycorrhizae Fig. 22.10 Ascomycetes – The Sac Fungi Ascomycetes (phylum Ascomycota) live in marine, freshwater, and terrestrial habitats Ascomycetes are commonly called sac fungi Ascomycetes include plant pathogens, decomposers, and symbionts (some ectomycorrhizae, found in lichens) The phylum is defined by production of sexual spores in saclike asci, usually contained in fruiting bodies called ascocarps Ascomycete Diversity Fig. 22.11 BatConservation Trust White-nose syndrome Pseudogymnoascus destructans is an Ascomycete  File:Penicillium Pengo.jpg Ascomycete Diversity Penicillium sp. – antibiotics used by the fungi to ward off competitors (such as bacteria) Hypomyces (an Asco) on Lactarius (a basidio) Tuber melanosporum, a truffle File:FeetFungal.JPG This is a ringworm! Trichophyton sp. Athlete’s foot Dogs and pigs are used to hunt truffles!: https://www.youtube.com/watch?v=-odRryWBFnA&feature=youtu.be Ascomycetes Ascomycetes also reproduce asexually by enormous numbers of asexual spores called conidia Conidia are not formed inside sporangia; they are produced asexually at the tips of specialized hyphae called conidiophores Conidia of Penicillium, Conidia of an one type of Ascomycete Ascomycete Fig. 22.15b  Typhula sp., a snow mould Basidiomycetes - the Club Fungi Basidomycetes (Basidiomycota) include mushrooms, puffballs, and shelf fungi, mutualists (some ectomycorrhizae), and plant para- sites, and are also called club fungi The phylum is defined by a clublike structure called a basidium, a transient diploid stage in the life Collecting hedgehogs cycle Basidiomycete Diversity  Basidiomycete Diversity Glow to attract insects Rusts Smuts Snow molds Pricey edibles Basidiomycetes The life cycle of a basidiomycete usually includes a long-lived dikaryotic mycelium In response to environmental stimuli, the mycelium reproduces sexually by producing elaborate fruiting bodies call basidiocarps (e.g., ‘dikaryotic’ mushrooms) The numerous basidia in a basidiocarp are sources of sexual spores called basidio- spores Basidiomycetes Basidiomycetes radiating out from a localized source, and not fairies, sometimes form Fairy Rings F. Morgan Psilocybe semilanceata – Liberty cap contains psilocybin Lichens A lichen is a symbiotic association between a photosynthetic microorganism and a fungus in which millions of photosynthetic cells are held in a mass of fungal hyphae Cladonia stellaris, Telemark Norway, R. Rea Fig. 22.21a Lichens Most fungi in lichen are Ascomycetes! But Basidiomycete yeasts are often present! Fig. 22.21 A foliose lichen Aspen covered in lichen, RV Rea Lobaria, Roy Rea, Ancient Forest Lichens Some fruticose lichens Ole Husby Usnea sp. Old man’s beard Alectoria sp. Witch’s hair Bryoria sp. Horse’s hair Symbioses / Parasitisms Some fungi live in herbivore guts and help them break down cellulose Others live symbiotically (or not) with (or in) other organisms such as ants and plants Fig. 22.22 http://www.youtube.com/watch?v=Qb62Fikla2Q http://www.youtube.com/watch?v=R5piJCyHwtw