Mycology

Study of fungi

Fungi characteristics

Kingdom: fungi
Nutritional type: chemoheterotroph
Multicellularity: All, except yeasts
Cellular Arrangement: Unicellular, filamentous, fleshy
Food acquisition method: absorptive
Characteristic features: sexual and asexual spores

Fungi vs Bacteria Cell type

Fungi: Eukaryotic
Bacteria: Prokaryotic

Fungi vs Bacteria Cell Membrane

Fungi: sterols present
Bacteria: sterols absent, except in Mycoplasma

Fungi vs Bacteria Cell wall

Fungi: Glucans, mannans, chitin (no petidoglycan)
Bacteria: Peptidoglycan

Fungi vs Bacteria Spores

Fungi: sexual and asexual reproductive spores
Bacteria: Endospores (not for reproduction), some asexual reproductive spores

Fungi vs Bacteria metabolism

Fungi: limited to heterotrophic; aerobic, facultatively anaerobic
Bacteria: Heterotrophic, autotrophic, aerobic, facultatively anaerobic, anaerobic

Fungi characteristics in life:

-Pathogen in people with compromised immune system
-Nosocomial
-Beneficial because they decompose dead plants (with cellulase), plants are dependent on symbiotic fungi called mycorrhizae to absorb minerals and water, and can be eaten as food (mushrooms, b

Vegetative structure of fungi

refers to fungal colonies that grow

Thallus - fungi

body of fleshy fungi consist of long filaments

Hyphae - fungi

the long filaments
Two kinds:
1. Septate - have septum
2. Coenocytic - no septum

Vegetative hyphae

hyphae that absorbs nutrients

Reproductive/Aerial hyphae

Hyphae used for reproduction

Mycelium

mass of hyphae that makes it visible to the naked eye

Molds - fungi

The fungal thallus (body) consists of hyphae

Yeasts - fungi

Unicellular, nonfilamentous
-if buds fail to detach, it forms short chain of cells called pseudohyphae (Candida albicans)
-In the absence of O2, they ferment
Carbohydrates --> alcohol + CO2
(used in brewing, wine making, and bread)

Fission yeasts

some divide symmetrically
(Schizosaccharomyces)

Budding yeasts

divide asymmetrically
(Saccharomyces)

Fungal Dimorphism

Pathogenic dimorphic fungi are yeast-like at 37 C and mold-like at 25 C

Life Cycle of Fungi

-Asexual by fragmentation of hyphae or spores
-Sexual by spores
-Fungi are identified/classified as spores
-Spores are for reproduction, unlike bacterial endospores that are for survivals

Asexual Spores

formed by hyphae of one organism and germinate producing a similar organism

Sexual Spores

Formed by fusion of nuclei from two opposite mating types of the same species
--> organism will have genetic characteristics of both

Asexual reproduction of fungi

two types:
1. Conidiospore/Conidium --> not enclosed in a sac --> produced in chain at the end of conidiophore (Aspergillus flavus)
2. Sporangiospores --> formed within a sac called Sporangium --> located at the end of an aerial hyphae called sporangiopho

Asexual Reproduction - Conidiospore - Arthroconidia

Formed by fragmentation of hyphae
(Coccidioides immitis)

Asexual Reproduction - Conidiospore - Blastoconidia

formed by budding
(Candida albicans, Cryptococcus)

Asexual Reproduction - Conidiospore - Chlamydoconidia

thick-walled spore formed within the hyphae
-A cell rounds and enlarges
(C. albicans)

Sexual Reproduction of fungi

Consists of three phases:
1. Plasmogamy
2. Karyogamy
3. Meiosis

Plasmogamy

Haploid nucleus of donor cell (+) penetrates cytoplasm of recipient cell (-)
--> (+) and (-) are mating types

Karyogamy

(+) and (-) nuclei fuse to form diploid zygote

Meiosis

Diploid nucleus produces haploid nuclei (sexual spores)

Haploid

An organism or cell having only one complete set of chromosomes.

Diploid

2 sets of chromosomes

Zygospores (sexual spores)

Fusion of haploid cells produce one zygospore

Ascospore (sexual spores)

Formed is a sac (ascus)
(Talaromyces)

Basidiospore (sexual spores)

Formed externally on a pedestal called basidium

Fungi preferences

-Prefer pH 5
- molds are aerobic
-yeasts are facultative anaerobe
-more resistant to high osmotic pressure
-can grow on low moisture content
-can breakdown complex molecules --> why they grow in odd places (bathroom walls, shoe leather, newspapers)

Medically important phyla of fungi

-Zygomycota
-Ascomycota
-Anamorphs (Deutromycota)
-Basidiomycota

Zygomycota

-Conjugation fungi
-Coenocytic
-Saprophite
-Reproduction:
1. Sporangiospores (asexual)
2. Zygospores (sexual
--> Rhizopus stolonifer (black bread mold)

Life cycle of an asexual zygomycete

1. Aerial hypha produces a sporangium
2. Sporangium bursts to release spores
3. Spore germinates to produce hyphae
4. Vegetative mycelium grows

Life cycle of a sexual zygomycete

1. gamete forms at tip of hypha
2. Plasmogamy
3. Zygospore forms
4. Karyogamy and meiosis
5. Zygote produces a sporangium
6. Spores are released from sporangium
7. Spore germinates to produce hyphae

Ascomycota

-Sac fungi
-includes molds with septate hyphae and some yeasts
-Teleomorphic fungi: produce both sexually and asexually
-Conidiospores: asexual (dust)
-Ascospores: sexual and produced in a sac called Ascus (talaromyces)

Life cycle of an asexual ascomycete

1. hypha produce conidiophore
2. conidia are released from conidiophore
3. conidium germinates to produce hyphae
4. Vegetative mycelium grows

Life cycle of a sexual Ascomycete

1. Vegetative mycelium grows
2. Plasmogamy
3. Karyogamy
4. Meiosis then mitosis
5. Ascus opens to release ascospores
6. Ascospore germinates to produce hyphae

Anamorphs

-ascomycetes that have lost the ability to produce sexually
-produce asexual spores only
--> rRNA sequencing places most in Ascomycota and a few in Basidiomycota in this group (penicillium)
-Sporothrix (subcutaneous mycosis)
-Stachybotrys, Coccidioides, P

Basidiomycota

-Club fungi
-Septate
-produce mushrooms
-Basidiospores are formed on Basidium
-Some produce conidiospores (cryptococcus neoformans)
--> found in droppings of pigeons and transmitted by inhalation (airborne)
--> causes meningitis with high mortality rate

Life cycle of an asexual basidiomycete

1. Hyphal fragment breaks off vegetative mycelium
2. fragment grows to produce new mycelium
3. vegetative mycelium grows

Life cycle of a sexual basidiomycete

1. Vegetative mycelium grows
2. Plasmogamy
3. Fruiting structure ("mushroom") develops
4. Basidiospores are formed by meiosis
5. Basidiospores mature
6. Basidiospores are discharged
7. Basidiospore germinates to produce hyphae

Desirable economic effects of fungi

1. Saccharomyces cerevisiae used in:
-wine, bread, beet
-genetic engineering to produce hepatitis B vaccine
2. Torulopsis: protein supplement
3. Trichoderma: produces cellulase
4. Taxomyces: produces Taxol (anticancer)
5. Biological control of pests
--> E

Undesirable economical effects of fungi

1. spoil food: grow on jam, jellies and fruits
2. Dutch Elm disease caused by Ceratocystis ulmi
- in 1800, one million people died in Ireland due to starvation because potato crop failed due to Phytophthora infestans

Fungal diseases (mycoses)

1. Systemic mycoses: deep within body
-inhalation of spores: starts in lungs
-Histoplasma capsulatum causes Histoplasmosis
2. Cutaneous mycoses (dermatomycosis): affect hair, skin, and nails
- Dermatophytes
- dermatophytes produce keratinase
--> Microspor

opportunistic fungal diseases (mycoses)

1. Stachybotrys:
-grows on cellulose and water-damaged walls
-produces toxic spores that causes pulmonary hemorrhage
2. Pneumocystis
-causes pneumonia in AIDS patients

Lichens

-Mutualistic symbiosis between an algae (or cyanobacterium) and fungus
-Algae produces and secretes carbohydrates; fungus provides holdfast
-Survival is dependent on each other

Three types of symbiotic relationships

1. Mutualism
2. Commensalism
3. Parasitism

Mutualism

Both organisms benefit
-bacteria in human colon

Commensalism

one organism benefits, the other neither benefits nor is harmed
-Staphylococcus on skin

Parasitism

One organism benefits, the other is harmed
-tuberculosis bacteria in human lung

lichen thallus

-fungal hyphae grows around algae cells to form Medulla
-fungal hyphae also produces cortex

Three types of lichens

crustose, foliose, fruticose

Economic effects of lichens

-used as dye in litmus paper used for pH
-antimicrobial (produced by Usnea)
-used as dyes for clothing

Mycotoxins

-Toxins produced by fungi

Mycotoxins - Stachybotrys

produces Trichothecenes --> stops protein synthesis

Mycotoxins - C. albicans and Trichophyton

secrete protease

Mycotoxins - Claviceps purpurea

causes the disease ergotism by producing toxin ergot (acts like LSD causing hallucination)

Mycotoxins - Aspergillus

produces aflatoxin which is a carcinogen
-peanut butters are sometimes recalled for this

Mycotoxins - Amanita phalloides

commonly known as death angel produces neurotoxin

Algae characteristics

-mostly aquatic
-unicellular or multicellular
-photoautotroph (chlorophyll)
-Body of multicellular is called Thallus
-Holdfast: anchors the algae to rock
-Absorbs nutrients over entire surface
-Produce sexually and asexually
-Agar is extracted from red al

Life cycle of asexual unicellular algae

cell divides by mitosis and produces new cells (cytokinesis)

Life cycle of a sexual unicellular algae

gametes fuse (fertilization) to form Zygote

Rhodophyta - algae

-red algae
-cellulose cell walls
-most are multicellular
-store glucose polymer
-harvested for agar and carrageenan (food industry)

Chlorophyta - algae

- green algae
-cellulose cell walls
-unicellular or multicellular
-store glucose polymer

Diatoms - algae

-unicellular or filamentous
-pectin and silica cell walls
-fossilized diatoms formed oil
-some are poisonous by producing domoic acid (neurotoxin)
--> causes diarrhea and memory loss
--> transmitted to human by eating mussels that fed on poisonous diatoms

Dinoflagellates or Planktons - algae

-unicellular algae
-free floating organisms
-genus Alexandrium produces neurotoxin called saxitoxins
--> causes paralytic shellfish poisoning (PSP)
-produce 80% of Earth's oxygen

Protozoa characteristics

-unicellular
-kingdom: protist
-Mostly chemoheterotroph
-some are normal flora of animals
-some forms cysts under harsh conditions

Protozoa asexual life cycle

Asexually by:
-fission
-budding
-schizogony (multiple fission): nucleus divides into many and each forms a cell

Protozoa reproduce sexually by:

1. Conjugation:
-each cell has a macronucleus and a micronucleus
-Haploid micronucleus migrates to other cell and fuses with haploid macronucleus
2. Gamete (gametocyte) production:
-Gametocytes which are haploid fuse to form zygote (diploid)
Trophozoite i

Classification of protozoa

Based on locomotion:
1. Sarcodina: Pseudopod (amoeba)
2. Ciliophora: Cilia (paramacium)
3. Mastigophora: Flagella (Euglena)

Nutrition of protozoa

-some absorb through plasma membrane
-some have mouth called cytosome
-some by phagocytosis (Amoeba)
-Digestion takes place vacuoles

Medically important phyla of protozoa

Archaezoa
Microspora
Amoebozoa
Apicomplexa
Ciliophora
Euglenozoa

Archaezoa - protozoa

-no mitochondria
--> Have mitosome: remnant of mitochondria
-Multiple flagella
-Trichomonas vaginalis
--> infects female vagina
--> no cyst stage
--> transmitted by intercourse
-Giardia lamblia
--> cyst found in feces
--> causes giardiasis

Microspora - protozoa

-no mitochondria
-Obligate intracellular parasites
-reported since 1984 to be responsible for chronic diarrhea in AIDS patients

Amoebozoa or Amoebas - Protozoa

-move by pseudopods
-Entamoeba histolytica is the only pathogen and causes amoebic dysentery
--> transmitted by cyst
-Acanthamoeba: grows in water and infects cornea and causes blindness
--> unsanitary disinfecting of contact lenses

Apicomplexa - protozoa

-obligate intracellular parasites
-complex live cycle --> have several hosts
-Tips contain enzyme to penetrate host's tissue
--> plasmodium: causes malaria that is transmitted by mosquito Anopheles
--> Anopheles harbors infective stage called Sporozoite

Life Cycle of asexual Plasmodium vivax

1. Infected mosquito bites human, sporozoites migrate through bloodstream to liver of human
2. Sporozoites undergo schizogony in liver cell; merozoites are produced
3. Merozoites released into bloodstream from liver may infect new red blood cells
4. Meroz

Life Cycle of Sexual Plasmodium vivax

1. Another mosquito bites infected human and ingests gametocytes
2. In mosquito's digestive tract, gametocytes unite to form zygote
3. Resulting sporozoites migrate to salivary glands of mosquito

Cryptosporidium - protozoa

-another apicomplexan
-lives inside the cells lining small intestine
-causes diarrhea (gastroenteritis) by ingesting oocyst in contaminated water
-transmitted through feces of cows, cats and dogs
-sporozoites are visible inside oocyst
-resistant to most c

Cryptosporidium: prevention

-don't swim during and for 2 weeks after diarrheal illness
-avoid swallowing pool water
-wash hands after using the restrooms or changing diapers

Apicomplexa illnesses

-Toxoplasma Gondii
--> intracellular parasite of humans
--> life cycle involves cats
--> Trophozoite (vegetative) is called Tachyzoite that produces oocyst (contain sprozoite)
--> oocysts are excreted in cat feces
-Cyclospora cayentanensis
--> causes diar

Ciliates or Ciliophora - protozoa

-moved by cilia
-complex cells
-Balantidium coli is the only human parasite causing dysentery
-Cyst is ingested by host

Euglenozoa - protozoa

- move by flagella
1. Euglenoids are photoautotrophs and have red eyespot
2. Hemoflagellates are blood parasites that are transmitted by insects
-Trypanosoma gambiense causes African Sleeping sickness by Tsetse fly
-T. cruzi causes Chagas' disease by "kis

Slime Molds

-have fungi and amoeba characteristics
-two taxa:
1. Cellular
2. Plasmodial

Life cycle of cellular slime mold

1. amoeba grows and divides
2. when conditions unfavorable, they secrete cAMP
3. cAMP cause aggregation that forms "slug"
4. Slug moves towards light, and forms stalk and spores
5. Spores are released and germinate to complete the cycle

Plasmodial Slime Molds

-exists as a mass of protoplast with many nuclei (multinucleated)
-life cycle include both asexual and sexual reproduction