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The Eukaryotes
Chapter 12
BIO 220
Fig. 12.1
Fungi
• Of the more than 100,000 species of fungi, only
about 200 are pathogenic to humans and
animals
• Decompose dead plant matter (saprophytic),
allowing the recycling of elements
• Nearly all plants depend on symbiotic fungi
called mycorrhizae
• Humans use fungi for food, to produce foods,
and drug production
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Characteristics of fungi
Characteristics of fungi
• The body or thallus of molds and fleshy fungi
is made of many hyphae
• Vegetative hyphae obtain nutrients
• Aerial hyphae are concerned with reproduction
• A mycelium can form if conditions are right
Fig. 12.2a
Fig. 12.3
Yeasts
Some fungi produce pseudohyphae
• Nonfilamentous, unicellular fungi
• Can be found as a white powder on fruits and
leaves
• Many reproduce by budding (i.e. S. cerevisiae)
Fig. 12.4
Fig. 21.17
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Yeasts cont.
Dimorphic fungi
• Schizosaccharomyces reproduces by fission
• Parent cell elongates, its nucleus divides, and
two offspring cells are produced
• Yeasts are facultative anaerobes which allows
them to survive in a variety of environments
Fig. 12.5
Reproduction of Fungi
Asexual spores
• Filamentous fungi can reproduce asexually by
fragmentation of their hyphae
• Are formed from the hyphae of one organism
• Asexual spores are produced through mitosis
and subsequent cell division
• When these spores germinate, they produce
organisms that are genetically identical to the
parent
• Two types of asexual spores are conidiospores
and sporangiospores
• Fungi also reproduce by the formation of
spores (asexual AND sexual reproduction)
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Conidiospores
• Spores are unicellular or multicellular and NOT
enclosed in a sac
• Conidiospores are produced at the end of
conidiophores
Arthroconidia
• Conidia formed by the fragmentation of a
septate hypha into single, slightly thickened
cells
• Coccidioides immitis
Fig. 12.6
Blastoconidia
• Conidia formed from the buds of its parent
cell
Fig. 12.6
Fig. 12.6
Sporangiospores
• Spores form within a sac called a sporangium
which is at the end of an aerial hypa called a
sporangiophore
Fig. 12.6
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Nutritional requirements
Sexual reproduction is in three phases
• Plasmogamy
– Haploid nucleus of donor cell (+) enters cytoplasm
of recipient cell (-)
• Karyogamy
– Fusion of nuclei, so now have a diploid zygote
nucleus
• Meiosis
– Haploid nuclei (spores) will be formed
• Chemoheterotrophs
• Typically grow best in an environment pH=5
• Most molds are aerobic, most yeasts are facultative
anaerobes
• Can grow in relatively high sugar or salt
environment
• Can grow on substances with low moisture content
• Reduced nitrogen requirement
• Can metabolize complex carbohydrates
Zygomycota
Medically important fungi
• Zygomycota
• Saprophytic molds with have coenocytic hyphae
• Microsporidia
• Ascomycota
• Basidiomycota
Fig. 12.7
i.e. Rhizopus stolonifer
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Microsporidia
Ascomycota (sac fungi)
• Obligate intracellular parasites
• Lack mitochondria, no microtubules, obligate
parasites
i.e. Encephalitozoon
Fig. 12.8
• Molds with septate hyphae
• Yeasts
Fig. 12.9
Basidiomycota (club fungi)
• Septate hyphae
Anamorphs
• Fungi that have lost the ability to reproduce
sexually
• Most are members of Ascomycota
• i.e. Penicillium
i.e. Amanita phalloides
Fig. 12.10
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Mycoses
•
•
•
•
•
Systemic – infections deep in body
Subcutaneous – beneath the skin
Cutaneous – affect skin, hair, nails
Superficial – superficial epidermis, hair shafts
Opportunistic
Coccidioides immitis
• Etiological agent of coccidioidomycosis (San
Joaquin fever)
Figs. 24.17, 24.18
Cryptococcus neoformans
• Etiological agent of meningitis
• Widely distributed, especially in areas
contaminated by bird feces (esp. pigeons)
• Transmitted by inhalation of contaminated
droppings
• Most cases occur in people that are severely
immunocompromised
Claviceps purpurea
• Etiological agent of ergotism
• Plant pathogen that grows on grains (rye)
• Toxin (ergot) contained in sclerotia, causes
hallucinations resembling those produced by
LSD
• Constricts blood vessels, potentially causing
gangrene of limbs due to inadequate blood
flow
Fig. 22.15
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Pneumocystis
Dermatomycoses
• Dermatophytes colonize the hair, nails, and
outer layer of the epidermis
• Tinea capitis (ringworm), tinea cruris (jock
itch), tinea pedis (athlete’s foot)
• Trichophyton (hair, skin, nails)
• Microsporum (hair, skin)
• Epidermophyton (skin, nails)
• Opportunistic pathogen, which can cause
pneumonia in immunocompromised individuals
Fig. 24.19
Candidiasis
Fig. 21.17
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Benefits of fungi
• Saccharomyces – bread and wine
• Entomophaga – biological pest control
• Paecilomyces fumosoroseus – biological pest
control
• Antibiotic production
Lichens
Lichens
• Combination of a green alga (or cyanobacterium)
and a fungus
• Classified based on the fungal partner (usually
Ascomycota)
• Can survive in environments in which the alga or
fungus would be unable to survive alone
• Found on rooftops, trees, newly exposed dirt or
rock
Fig. 12.11
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