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Kingdom Fungi Chapter 21. Fungi: Friend or Foe Positives –Valuable decomposers –Make bread, beer, wine with help of yeast fungi –Antibiotics –Organ transplants.

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Presentation on theme: "Kingdom Fungi Chapter 21. Fungi: Friend or Foe Positives –Valuable decomposers –Make bread, beer, wine with help of yeast fungi –Antibiotics –Organ transplants."— Presentation transcript:

1 Kingdom Fungi Chapter 21

2 Fungi: Friend or Foe Positives –Valuable decomposers –Make bread, beer, wine with help of yeast fungi –Antibiotics –Organ transplants made possible by fungal molecules that suppress immune system –Saccharomyces cerevisiae Model in quest for cancer cures Genome first among eukaryotes to be sequenced Negatives –Attack crop plants, farm animals, and humans with costly results –Attack stored food, lumber, clothing

3 Characteristics of True Fungi Eukaryotes Chemoheterotrophs Chitinous cell wall –Gives shape to cell –Limits invasion by other organisms –Prevents cell from bursting under pressure –Prevents fungus from engulfing solid foods –Limits growth

4 Characteristics of True Fungi Reproduction –Spores Often released in large numbers Can resist dehydration Light enough to be carried by gentle breezes Remain dormant until reach moist environment containing food

5 Fungal Mycelia Multicellular body often called a thallus (plural, thalli) –Unique type of thallus called a mycelium Composed of branching tubes called hyphae (singular, hypha) –Injured mycelia capable of regeneration

6 Fungal Mycelia Cytoplasmic streaming –Carries food and organelles to hyphae Yeast lack mycelia Dimorphism –Occurrence of two growth forms –Switch between mycelial and yeast growth depending on growing conditions

7 Fungal Nutritional Needs Can make nearly all the molecules they need from a few raw materials Need water, a few minerals, an organic compound for carbon and energy, a few vitamins (including vitamin B 1 )

8 Fungal and Bacterial Competition Compete with each other for food Rapid growth of hyphae and mycelium is advantageous to fungus FungiBacteria Slower reproductive rate Reproduce quickly Fungal hyphae grow quickly into new territory; can rapidly move nutrients from buried feeding hyphae to aerial hyphae Slow to reach new food source after food is exhausted in immediate vicinity Growth of fungal mycelium is indeterminate Forms small colony; colony usually remains small

9 Fungal and Bacterial Competition Additional reasons fungi can outcompete bacteria –Fungi secrete acid as part of their feeding system Slows bacterial growth –Some fungi secrete antibiotics that poison bacteria Example: penicillin

10 Fungal and Bacterial Competition –Outcompete bacteria with help of superior food-digesting systems Example: some fungi have enzymes that degrade lignin to expose cellulose

11 Fungal Mycelium and Hyphae Growth of mycelium –indeterminate Hyphae make up mycelium –Types of hyphae Septate –Have cross walls called septa –Septa have septal pore (perforation) which allows materials to move between compartments Aseptate –Lack septa

12 Ecological Strategies of Fungi Symbiotic relationships –Mutualism  both partners benefit Mycorrhizae Lichens –Fungi and green algae or cyanobacteria Found in cow’s stomach –Digest cellulose and other substances cow lacks enzymes for Leaf-cutter ants –Feed on fungus

13 Ecological Strategies of Fungi –Parasitism  fungus benefits and host is harmed Attack other fungi or animals Most attack plants –Rusts, smuts Saprobes  organisms that feed on dead organic matter –Decomposers Recycle chemical elements by breaking down organic molecules

14 Ecological Strategies of Fungi –Opportunists Describes most saprobic fungi Exploit temporary opportunities such as a fallen fruit

15 Reproductive Strategies More than 1,000 species have swimming spores Most have spores that drift in air or water Most spores never reach food source

16 Reproductive Strategies Asexual ReproductionSexual Reproduction Mitospores produced through mitosis; example, conidia produced on conidiophores Meiospores produced through meiosis Faster, more economicalSlower, less economical Does not require partner Requires compatible cells or hyphae No genetic varietyGenetic variety

17 Reproductive Strategies Mitosporic fungi –Fungi that have never been seen to reproduce sexually –Sometimes show evidence of recombination of genes Parasexual cycle –Possible explanation for recombination –Only seen in laboratory –Lacks meiosis that typifies sexual reproduction –Heterokaryotic »Describes mycelium with nuclei of more than one genotype in uncontrolled proportions

18 Fungal Classification Mycologist –Scientist who studies fungi Updating fungal classification Molecular phylogenetic methods reveal –At least 1.5 million species –Only about 80,000 currently named

19 Fungal Classification True fungi –Monophyletic –Does not include the groups formerly included in original kingdom Fungi Oomycetes  egg fungi Acrasids  slime molds Mycetozoa  slime molds –DNA analysis suggests fungi are more closely related to animals instead of plants

20 Fungal Classification Endings for taxa –Phyla (or division) –mycota –Class – mycetes –Order – ales –Family - aceae Terrestrial fungi classified into phyla based on sexual reproduction Aquatic fungi set apart by flagellated reproductive cells

21 Fungal Classification PhylumSexual spore Sexual spore produced on or inside of Terrestrial or aquatic BasidiomycotaBasidiosporeBasidiumTerrestrial AscomycotaAscosporeAscusTerrestrial ZygomycotaZygosporeZygosporangiumTerrestrial Chytridiomycota (set apart by flagellated reproductive cells) Has not been observed to reproduce sexually Aquatic

22 Fungal Classification Fungal systematics – work in progress –Artificial phylum Deuteromycota eliminated –Ascomycota and Basidiomycota monophyletic –Zygomycota and Chytridiomycota probably not monophyletic

23 Fungal Classification –Steps toward making Zygomycota monophyletic 2001 Arthur Schübler and colleagues –Proposed moving group from Zygomycota to a new monophyletic group, the Glomeromycota »Members of Glomeromycota assist growth of about 80% of green plants through symbiotic associations with roots

24 Fungal Classification DikaryomycetesCoenomycetes Higher fungiLower fungi Ascomycota, Basidiomycota Chytridiomycota, Zygomycota, Glomeromycota 95% of named fungal species5% of named fungal species Septate hyphaeAseptate (coenocytic) hyphae Dikaryotic stage in sexual life cycle Never have dikaryotic stage, have haploid mycelia with only one version of each gene

25 Phylum Chytridiomycota About 1,000 named species Have swimming cells at some point in life cycle Need microscope to study None cause human disease Common in ponds and wet soil –Decompose organic matter –Attack algae, pollen grains, wet soil

26 Phylum Chytridiomycota Life cycle –Zoospore swims to food source, retracts or drops flagellum, forms cell wall, grows into a thallus –Rhizoids anchor thallus and absorb food –Thallus differentiates into one or more mitosporangia where mitospores are formed –Most mitospores function in asexual reproduction

27 Phylum Chytridiomycota –Sexual reproduction usually unknown –Occasionally rhizoids fuse, transfer nuclei between thalli or two swimming mitospores fuse –Fusion cell expands, forms meiosporangium where meiospores are formed –Nuclei fuse, divide by meiosis, form genetically diverse meiospores

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29 Phylum Zygomycota Have more in common with aquatic chytrids than other land fungi Approximately 1,100 zygomycete species named and described A few attack humans –Example: mucormycoses Many are saprobes –Recycle waste products

30 Phylum Zygomycota Many attack insects such as flies, termites, aphids Some parasitize other fungi and small animals such as nematodes Studied in detail because –reproductive hyphae are large and easy to observe –Very sensitive to environmental stimuli

31 Phylum Zygomycota Find mating partners by exchanging chemical signals called phermones –Phermones are also exchanged in chytrids, ascomycetes, and basidiomycetes

32 Phylum Zygomycota Life history of Rhizopus stolonifer –Asexual reproduction –Meiospore settles on food and grows into large, aseptate mycelium –Reproductive hyphae called sporangiophores grow into air Tip forms mitosporangium Produces mitospores Released when mature

33 Phylum Zygomycota –Sexual reproduction –Special hyphal tips of two different mating types meet –Cross walls form behind tips, walling off two cells called gametangia –Gametangia fuse, walls dissolve between them –Fusion cell called zygosporangium (meiosporangium)

34 Phylum Zygomycota Zygosporangium becomes zygospore –Rests for months –Meiosis converts 2n nuclei into recombinant 1n nuclei –Hypha grows out of zygospore Tip swells and forms germ sporangium –Recombinant nuclei incorporated into meiospores

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36 Phylum Glomeromycota Includes only about 157 named species Form symbiotic relationships known as mycorrhizae with more than 80% of wild plants –Endomycorrhizae (penetrate inside root cells) –Form characteristic structure called arbuscule Formerly classified in Zygomycota Live in soil

37 Phylum Glomeromycota Aseptate hyphae Sexual reproduction unknown Make asexual mitospores –Swollen tip of a hypha

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39 Phylum Ascomycota More than 32,000 named species At least 58 genera have members that cause disease –Athlete’s foot, jock itch, ringworm Grow in dead layers of skin –Coccidioides immitis Initial lung infection can spread to other parts of body Can be fatal in some patients

40 Phylum Ascomycota –Pathogenic species especially dangerous in individuals with compromised immune system (AIDS, organ transplant patients) Pneumocystis carinii (Pneumocystis jiroveci) –Fatal pneumonia in AIDS patients Candida albicans –common yeast found in mouth and vagina »Overgrowth in mouth called thrush (often signals transition to full-blown AIDS) »Bacteria normally keep population in check

41 Phylum Ascomycota –Fungal diseases in plants Powdery mildew –Four ascomycetes that helped scientists win Nobel Prizes Neurospora crassa –Studies first revealed that genes control protein synthesis Penicillium notatum –Antibiotic penicillin Saccharomyces cerevisiae –Improved understanding of cell division Schizosaccharomyces pombe –Improved understanding of cell division

42 Phylum Ascomycota Production of food and beverages –Saccharomyces cerevisiae Used in baking and brewing –CO 2 and alcohol from alcoholic fermentation –Morchella Morel (edible) –Tuber Truffle (edible)

43 Phylum Ascomycota Life cycle – asexual reproduction –1n spore lands on food source, forms mycelium –Produces asexual conidia on aerial hyphae –Spores produced by conidia

44 Phylum Ascomycota Sexual reproduction –Meeting of plus and minus mating types causes both to make female ascogonia and male antheridia –Antheridia of one mycelium fuses with ascogonia of other mycelium –Fruiting structure called an ascoma (plural, ascomata) forms

45 Phylum Ascomycota –Tip of hypha bends as it grows and forms a crozier (this forms the ascus) –Hyphae on one side of ascoma produce meiosporangia called asci –Ascospores formed in asci Vary in method of release

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47 Phylum Ascomycota Steps in asci formation –Ascogenous hypha forms crozier –1n nuclei in crozier divide by mitosis –Septa divide crozier into three cells –Crozier’s tip cell fuses with hyphal stalk restoring n + n condition to stalk cell –Karyogamy occurs in ascus to make 2n zygote nucleus

48 Phylum Ascomycota –Meiosis produces four recombinant 1n nuclei in first ascus –Cell below first ascus grows n + n hypha that forms new crozier –Mitosis doubles number of 1n nuclei in first ascus –Second crozier repeats above steps to make a second ascus –Spores mature in first ascus while second ascus goes through meiosis and a third ascus forms

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50 Phylum Ascomycota Main types of ascomata –Apothecium Resembles open cup Ascus shoots spores upward for dispersal –Perithecium Nearly closed, like a flask Pore at small end opens to release spores –Cleistothecia Tiny closed spheres that dry up and shelter enclosed asci until cleistothecium is crushed Spores shot away or passively released

51 Phylum Ascomycota Symbiotic ascomycetes –Truffles Tuber Underground ascomata Ectomycorrhizae –does not enter plant cells but coats root tip and grows between root cells –Assists plant in bringing in nitrogen compounds and water

52 Phylum Ascomycota –Lichens Symbiotic relationship between ascomycete and algae and/or cyanobacteria –Debate over whether relationship is mutualistic or parasitic At least 42% of named ascomycetes take part in lichens Pioneers in rocky areas without soil –Begins soil formation process

53 Phylum Ascomycota –Lichens named for fungal component –Types of lichens Foliose –Leaf-like Fruticose –Branching Crustose –Crusty; form green, yellow, red, or oranges patches on bark, posts, and rocks

54 Phylum Ascomycota –Reproduction Most reproduce asexually –May release units called soredia (singular, soridium) –May fragment or pinch off forming isidia (singular, isidium) –May produce conidia Sexual reproduction –Fungal partner makes asci and algal partner undergoes genetic recombination

55 Phylum Ascomycota Many Ascomycota are dimorphic –Switch between mycelial and yeast forms in response to environment Histoplasma capsulatum – yeast in body and mycelium outside body Candida - mycelium in body and yeast outside body

56 Phylum Ascomycota Additional example of Ascomycota –Aspergillus Causes food decay Causes respiratory disease called aspergillosis Aspergillus flavus –Produces cancer-producing compounds called aflatoxins Other species –Used in production of soy sauce and industrial chemicals such as citric acid

57 Phylum Basidiomycota More than 26,000 named species Three classes –Hymenomycetes –Ustilaginomycetes –Urediniomycetes

58 Phylum Basidiomycota Hymenomycetes –Contains more than 14,000 named species –Includes most conspicuous members of Basidiomycota such as mushrooms –Usually produce spores sexually Use meiospores to multiply and diversify

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60 Phylum Basidiomycota –Fruiting body Basidiomata (singular, basidioma) Basidium forms at tip of hyphae Wall of basidium produces stalk called sterigma Tip of sterigma produces basidiospores –Different types of fruiting bodies Bracket or shelf fungi –Have caps like mushrooms but no stipe Puffballs –make spores inside leathery bag

61 Phylum Basidiomycota Bird’s nest fungus –Makes basidiomata that look like tiny nests with eggs Coral fungi –Make basidiomata that resemble reef corals and release spores all over the surface Jelly fungi –Basidiomata has supporting tissues with delicate gelatinous texture

62 Phylum Basidiomycota Some basidiomata produce huge numbers of spores –Grocery store mushroom, Agaricus bisporus, makes 40 million spores every hour for 2 days –Shelf fungus that attacks trees, Ganoderma applanatum, can make 3 billion spores per day for 6 months each year –Puffball, Calvatia gigantea, may produce 7 trillion spores

63 Phylum Basidiomycota Amanita – poisonous mushroom Some are important mycorrhizal partners of forest trees –Ectomycorrhizae Many are saprobes –Decompose dead wood and leaves Can attack wood in houses causing dry rot

64 Phylum Basidiomycota Ballistospore release –Gentle method for releasing spores –Occurs in all major groups of Basidiomycota

65 Phylum Basidiomycota Class Ustilaginomycetes –Includes 1,064 names species –Most attack green plants Usually result in diseases called smuts Ustilago maydis causes smut disease in corn –Most smut fungi live as yeasts in haploid stage and parasitic mycelia in dikaryotic stage

66 Phylum Basidiomycota Class Urediniomycetes –Includes more than 8,000 names species –Complex life cycles Many have two hosts –Diseases they cause are called rusts Difficult to eradicate because of the two hosts Approaches to controlling –Breed new varieties that are resistant to common strains of rust –Eliminate other host


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