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Chapter 26

The Fungi (Eumycota) 12-02-0812-03-08

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Fungal Subdivisionssequence of 18S rRNA and some protein coding genes indicates the Fungi are a monophyletic group with eight divisions

ChytridiomycetesZygomycotaAscomycotaBasidiomycotaUrediniomycetesUstilaginomycetesGlomeromycotaMicrosporidia Figure 26.1

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True fungi

fungus (pl., fungi)Eucaryotic cellspore-bearingchemoorganoheterotrophsreproduce sexually and asexuallybelong to kingdom Fungi (Eumycota) within domain Eucarya

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Some terms

mycologystudy of fungi

mycologistsscientists who study fungi

mycotoxicologystudy of fungal toxins and their effects

mycosesdiseases caused by fungi

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Nutrition and Metabolismmost are saprophytes

obtain nutrients from dead organic materialsecrete hydrolytic enzymes

chemoorganoheterotrophsglycogen is primary storage polysaccharidemost are aerobic

some are facultative anaerobesobligate anaerobic fungi are found in rumen of cattle

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Importancebeneficial impact

decomposersindustrial fermentations

Foods- mushroomfermented foods and beveragessteroids, antibiotics and other drugs

Research (Saccharomyces cerevisiae)model eucaryotic organisms

detrimental impactmajor cause of plant diseasescause of many animals including human diseases

7Table 26.1

Mycotoxicoses

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Distributionprimarily terrestrial

few aquatic speciessome form associations

mycorrhizae – associations with plant rootslichens – associations with algae or cyanobacteria

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Fungal Structure

Thallus- body or vegetative structurecell walls usually composed of chitin

polysaccharide consisting of N-acetyl glucosamine residues

have two reproductive structuressporangia form asexual sporesgametangia form sexual gametes

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Yeastunicellular fungireproduce asexually, often by buddingreproduce sexually by formation of spores

Figure 26. 4

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Moldsfilamentous fungi

hyphae (s., hypha)the filaments of a moldmay be coenocytic (no cross walls) or have septa (cross walls)

mycelium (pl. mycelia)bundles or tangled masses of hyphae

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Dimorphismsome fungi change from yeast form (Y) to mold form (M): YM shiftin plants, M in host and Y outside hostin animals, Y in host and M outside host

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Asexual reproductiontransverse fissionbuddingspore production

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Sexual reproductioninvolves union of compatible nuclei followed by formation of sexual spores (zygospores, ascospores, or basidiospores)zygote formation

several mechanismsfusion of gametesfusion of gametangia

gamete-producing bodiesfusion of hyphae

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ChytridiomycetesOomycetesSimplest, free-living and parasitic formsproduce zoospores with single, posterior, whiplash flagellum asexual and sexual reproductionmany can degrade cellulose and keratin

Allomyces

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Division Zygomycota- Zygomycetes

coenocytic hyphaecontaining numerous haploid nuclei

- most are saprophytesa few are plant and animal parasites

- some of industrial importance

Rhizopus stolonifer, Mucor sppfoods, antibiotics and other drugs, meat tenderizer, and food coloring

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Glomeromycota

Previously considered as zygomycetesmajor importance as endomycorrhizalsymbionts of vascular plants

form intracellular associations within roots of almost all herbaceous plants and tropical trees

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Ascomycotaascomycetes (sac fungi)

during sexual reproduction produce ascus (pl., asci) containing haploid ascospores

considerable human impactfood spoilage and plant diseasesedible mushrooms, and food and beverage productionModel organism for cell biology, genetics, cancer research

can be filamentous or yeast formfilamentous forms have septate hyphae and asexual reproduction by conidiospores

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Ascomycetes- considerable human impact

Ergot (Claviceps purpurea) and ErgotismErgot alkaloids

LSD (lysergic acid diethylamide), oxytocin, to ease migraine

food spoilage, plant and animal diseasesedible mushrooms, and food and beverage productionresearch

The black Truffle

Morel-Morchella

Truffle-Diamonds of the Kitchen

Chocolate truffleThe highly-prized ingredient used in European cooking which is famous for its unique smell can sell for up to NT$180,000 a kilogram

常春藤解析英語 10-07-2008

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Division Ascomycotaascomycetes – sac fungi

sexual reproduction produce ascus (pl., asci) containing haploid ascospores

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Sexual cycle of Ascomycetes

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Reproduction cycle- Saccharomyces

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Asexual reproduction- Aspergillus

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Basidiomycotabasidiomycetes (club fungi)

during sexual reproduction form basidiumhuman impact

decomposersedible mushroomspathogens of humans, other animals, and plants

Cryptococcus neoformans – cryptococcosissystemic infection, primarily of lungs and central nervous system- aseptic meningitis

Amanita phalloides- destroying Angelproduce phalloidin and amanitin neurotoxin

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Life cycle of Basidomycetes

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Urediniomycetes and Ustilaginomycetesplant pathogens causing “rusts” and “smuts’

Ustilago maydis- tumor formation in corn

- some Urediniomycetes are also human pathogens

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Microsporidiaare still sometimes considered protistshave a unique morphology

lack mitochondria, peroxisome, centriole

obligate intracellular parasites that infect insects, fish, and humans

Microsporidian spore

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Chapter 39

Human Diseases Caused by Fungi - Mycoses

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Superficial Mycoses

Piedras- infections of hair shaft

髮癬 鬚癬

毛幹結病

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Cutaneous MycosesDermatomycoses, ringworms, and tineas-distinguished according to causative agent and area of body affected

Tinea Barbae; T. capitis ; T. corporis ; T. cruris ; T. pedis ; T. unguium - onychomycosis

most common fungal diseases, occurring worldwidetreatment, prevention, and control

microscopic examination (under Wood’s light) of skin biopsies and culture on Sabouraud’s

glucose agartopical ointments and antifungal agents

Tineas 癬

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Subcutaneous Mycoses (1)caused by saprophytic inhabitants of soilintroduced in soil-contaminated puncture woundsclinical manifestations

develop slowly over a period of yearsnodules form and ulcerateorganisms spread along lymphatic channels, producing more nodules

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Subcutaneous Mycoses (2)Chromoblastomycosis

formed dark brown nodulesmost infections involved legs and feet

Maduromycosisprevalent in tropicseumycotic mycetoma (madura foot)

Sporotrichosismost common in USAan occupational diseaseextracutaneous sporotrichosis

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Systemic Mycoses (1)most are caused by dimorphic fungi (YM shift)acquired by inhalation of spores from soilpulmonary syndromes- through blood stream to other organsCryptococcus neoformansonly has yeast form- a large capsule

Cryptococosis- worldwide distributionfound in 15% AIDS patientscause pulmonary, skin, bone and CNS infections

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Systemic Mycoses (2)Endemic infections- most are asymptomaticBlastomycosis (Fig. 40.10)

predominant in Mississippi and Ohio river

Coccidioidymycosis (Coccidioides immitis)valley fever or desert rheumatism arthrocinidia and endospore Fig. 40.11

HistoplasmosisIntracellular infections Macrocinidia and microconidiayeastlike cells in macrophage

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Opportunistic Mycoses (Table 39.1)

opportunistic microorganismnormally harmless but becomes pathogenic in compromised hostmalnutrition, alcoholism, cancer, diabetes, leukemia, and others…

Aspergillosisin severely compromised individuals, lungs may fill with mycelia- brocho pulmonary aspergillosisAspergilloma - fungus ballA. flavus and A. fumigatus

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Candidiasis- An important nosocomial infection

produce a diverse spectrum of diseasesoral candidiasis (thrush)paronychia and onychomycosisintertriginous candidiasis

- axillae, groin, and skin foldsnapkin (diaper) candidiasis

candidal vaginitis: when lactobacilli are depleted

listed by CDC as a STD (Sexually transmitted diseases)

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Microsporidia- Microsporidosis

Found mostly in HIV patientsSeveral domestic and feral animals are reservoirsProduce highly resistant sporeCause a wide variety of diseases including hepatitis, pneumonia, skin lesions, diarrhea, weight loss, and wasting syndromes

Fig. 39.27

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Pneumocystis Pneumonia

Pneumocystis carniipneumonia – PCPP. jiroveci

A protist? - classified into fungi on the basis of rRNA and DNA sequences Occurs exclusively in immunocompromisedpatientscommon in AIDS patients

Fig. 39.28

The Protists

Chapter 25

The Protists

Protistology

most are unicellular

lack the level of tissue organization

usually reproduce asexuallybinary fission

Polyphyletic

an artificial grouping of over 64,000 single-celled life formsprotozoa

chemoorganotrophic protistsprotozoology

algaephotosynthetic protistsphycology

Four major groups

Classified by means of local motionFlagellates, Ciliates, and Amoebae

many protists have cilia or flagella at some point in life cycle formation associated with kinetosomeplays role in motilityalso used to generate water currents for feeding and respiration

Sporozae (Stationary forms)

Distribution

a wide variety of moist habitats- terrestrial and planktonic formsmost are free livingplay role in recycling nitrogen and phosphorusparasitic forms cause disease in humans and domesticated animals

Table 25.1

Nutrition

Photosynthetic protists are aerobicoxygenic photosynthesis with photosystems I and II

Chemoheterotrophic protistsholozoic- acquired nutrients by phagocytosissaprozoic- acquired nutrients by endocytosis, diffusion or carrier mediated transport

osmotrophy –soluble nutrients are assimilated

Mixotrophy

Figure 25.2

Holozoic feeding

Structure

plasmalemma- protist cell membranecytoplasm

ectoplasm and endoplasmcontractile, secretory and phagocytic vacuolesenergy-conserving organelles

Mitochondria hydrogenosomes (anaerobes)

chloroplasts

Encystment and excystment

Cyst (thick-walled resistant resting cell)Encystation

some protozoa secrete resistant covering A dormant form (very low metabolic activity)

Excystmentrelease from cyst triggered by favorable environmental conditions

Reproduction

binary or multiple fission or buddingsexual reproduction

conjugationsyngamyautogamy

Figure 25.3

Giardiasis-food and waterborne disease

International Society of Protistologists

FornicataMost bear flagella and lack mitochondria

Most are harmless symbionts

Some are free-living in waters that are heavily polluted with organic nutrients

Giardia intestinalis- first discovered by van Leeuwenhoek in 1681 in his own stool

Trichomoniasis (abortion) 陰道滴虫症

One of the most common sexually transmitted disease

7 million cases/y in USA and 180 million cases/y worldwide

caused by flagellated Trichomonasvaginalis

Fig. 39.21

Euglenozoa

commonly found in fresh water

Euglena

Fig. 25.5

A red eyespot helps to orient to light

Euglenozoa- Trypanosomes

parasites of plants and animalsleishmaniasis

caused by members of genus Leishmania

includes systemic and skin/membrane damage

Trypanosoma cruzicauses Chagas disease

transmitted by “kissing bugs＂

causes damage to nervous system

T. gambiense and T. rhodesiensecause African sleeping sickness

Fig.25.6- Tsetse flies

Leishmaniasis

Cause by flagellated protozoa and transmitted by sand flies from animals (canines and rodents)Leishmania braziliensis cause mucocutaneous leishmaniasis in tropical America

Produce lesions involving the mouth, nose, and skin and results in extensive scarring and disfigurement

L. donovani: endemic in areas within northern China, estern India, the Mediterranean countries, the Sudan, and Latin America

produces visceral leishmaniasis

L. tropica and L. mexicanainfections produce relatively small red papule at the site of insect bite eventually develop into crustated ulcers

Fig. 39.8

Tryanosomiasis 錐形虫症

African sleeping sickness

no suitable drug vaccines are not useful (phase variation of the protein coat to evade the immunologic response)

American trypanosomiasis

heart disease and other disorders no treatment available

Fig. 39.9

Amoebozoa

use of pseudopodia for locomotion and feeding

shape of pseudopodslobopodia – roundedfilopodia – long and narrow reticulopodia – form a netlike mesh

most amoebae reproduce by asexual divisionFree-living forms Inhabit almost any environment

Fig. 25.8 Amoeba proteus

Amebiasis- amebic dysentery

Fig. 39.22

Entamoeba histolyticaendemic in warm climates100,000 death/ y worldwidehighly variable symptoms:

asymptomatic infectionfulminating dysentery (exhaustive diarrhea accompanied by blood and mucus, appendicitis, and abscess in liver, lung, or brain)

Eumycetozoa- “Slime Molds＂

have been classified as plants, animals or fungi

Myxogastria-acellular slime molds

Plasmodium

Figure 25.9

Cell cycle

Dictyostelia- Cellular Slime Molds

Figure 25.10a

Dictyostelium discoideum

- A model organism

- formation of cellulose-walled macrocyst (> 40 genes involved in biosynthesis and degradation of cellulose)

- 33.8 Mbp genome

Apicomplexans

Apical complexparasitic life cycles

both sexual and asexual phases

clonal and sexual stages are haploid (except for zygotes)sporozoite is the motile, infective stage

most important member is Plasmodium, the cause of malaria

Figure 25.15

Life cycle of Plasmodium vivax

Asexual cycle in erythrocyte

- anemia, and hypertrophy of spleen and liver

Sexual cycle in mosquito

Fig. 39.5

Malaria- caused by the sporozoa Plasmodium

Human malaria caused by 4 species: P. falciparum, P. malariae, P. vivax, and P.ovale

300 million people infected / y, > 1 million deaths/ y in Africa, and ~1000 cases reported/ y in USA

transmitted by female Anopheles mosquito

shaking chills, then burning fever followed by sweating

Malaria- erythrocyte cycle

Toxoplasmosis 弓形虫症

Toxoplasma gondiiFound in nearly all animals and most birds

Cats are the host for completion of the sexual cycle

Animals shed cysts in the feces and the cysts enter another host by nose or mouth

also transmitted by the ingestion of raw or undercooked meat, congenital transfer (causing congenital defects- ~3000/ y in USA or death), blood transfusion, or a tissue transplant

most cases are asymptomatic

cause severe diseases in immunosuppressedpatients

a major cause of death in AIDS patients

Fig. 39.20

Cryptosporidosis 隱孢子囊虫症

Cryptosporidium (hidden spore cysts)

found in 90% of sewage samples, in 75% of river waters, and in 28% drinking waters

cause outbreak of waterborne diseases with 10 to 100 oocysts (remain viable for 2 to 6 months in a moist environment)

Cause prolonged, sever, and life threatening dirrhea in immunocompromised patients (AIDS)

Fig. 39.23

Dinoflagellates

large group found in marine plankton

cause phosphorescence and toxic blooms

symbiotic forms live in association with reef building corals

Ciliophora

found in both benthic and planktonic communities in water and soil systemsuse many cilia as locomotory and feeding organellesreproduction

asexual by transverse binary fissionsexual by conjugation (Fig. 25.18) Fig. 25.17

Chloroplastidaoften referred to as green algaehave chlorophylls a and b, and carotenoidsmany have cellulose cell wallsexhibit a diverse morphology

Chlamydomonas

a haploid nucleus, large chloroplast, conspicuous pyrenoid, and a stigma (eyespot, for phototaxis)

osmoregulation controlled by two small contractile vacuoles at flagella base reproduces by sexual and asexual reproduction