mycology virology
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Mycology-Virology
What are fungi?
• They’re the mushroom that we eat and those found in athlete’s foot
• Eukaryotic, spore-bearing, heterotrophic organisms that produce extracellular enzymes and absorb their nutrition.
Characteristics of Fungi
• Eukaryotic
• Multicellular (except Yeasts)
• Non-vascular organisms (Plants and Animals are vascular)
• Reproduce by means of spores– Both sexual and asexual
• Typically non-motile (except Chytrids which has a mobile phase)
Characteristics of Fungi• Cytoplasmic ultrastructure broadly similar
to plant cells, but differ significantly in kinds of organelles and structures
• Fungi are heterotrophic not autotrophic like plants
• Unlike animals (also heterotrophic), which ingest then digest, fungi digest then ingest (exoenzymes)
Characteristics of Fungi• Most fungi store their food as glycogen
(like animals); plants store food as starch
• Most fungi have very small nuclei, with little repetitive DNA
• Mitosis is generally accomplished without dissolution of the nuclear envelope (produces different type of microtubules during nuclear division
Cell wall containing Chitin
Nutritional Status of Fungi• Saprophytes
– Use non-living organic material– Important scavengers in ecosystems– Along with bacteria, fungi are important in
recycling Carbon, Nitrogen and essential nutrients
• Parasites– Use organic material from living organisms,
harming them in some way– Range of hosts: from single celled diatoms to fungi
to plants to animals to humans
Characteristics of Fungi
• Mutualists (symbionts)– Fungi that have mutualistically beneficial
relationship with other living organisms– Mycorrhizae: associations of fungi with plant’s
roots– Lichens: associations of fungi with algae or
cyanobacteria
Characteristics of Fungi
• Fungal cells occurring in branching filaments are called hyphae.– Vegetative hyphae– Aerial hyphae
• A mass of filaments is called a mycelium.
• Cross walls separate the cells in the hypha of many species of fungi (septa)
Fungal Form and Function
AnatomyHyphae and mycelium
HyphaeMycelium
• Coenocytic hyphae – lack cross walls– Also known as non-septate hyphae– Rhizopus stolonifer– Differentiates fungi from other eukaryotic cells,
how?
Septae
Septate hyphaAseptate hypha,a.k.a. coenocytic
Three ploidy types
Haploid – most fungal hyphae and all spores have haploid nuclei
Diploid – diploid nuclei are found transiently during the sexual phase (if present)
Heterokaryon – unfused nuclei from different parents occupying the same unit of hypha
Yeast cells
• Unicellular fungi that do not form hyphae or mycelia
• Oval cells measuring 5 to 10 um in diameter
• Reproduce both sexually and asexually
Yeast and Fungal forms
• Some fungi can form a mycelium under certain environmental conditions and revert to a yeast form under other environmental conditions
• Known as biphasic or dimorphic
• Candida albicans
Are there anaerobic fungi?
• Facultative anaerobes
• Fermentation
• Metabolism
• Glycolysis
• Industrial products: ethyl alcohol, beer, wine, liquor (other products?)
• Saccharomyces cerevisiae
• Aspergillus niger
Reproduction
• Sexual and Asexual means
• Role of spores
• Asexual reproduction– Spores have identical genetic make-up– Does not need to involve union of sex cells– Budding?
Fungal Form and Function
Reproduction
Asexual – default mode under stable
conditions; spores are produced
Sexual – usually only under stressful
conditions; spores are produced;
many mating types possible
(essentially like having many different
sexes or genders)
Sexual Reproduction
• Begin with the production of haploid gametes (produced by parent fungal cells of opposite sexual types)
• Gamete production occurs by meiosis
• Gametes fuse to form diploid cell called zygote
• Gametes are either male (plus) or female (minus)
Sexual reproduction in fungi
zygotes (2n)
fusion of compatible hyphae(plasmogamy)
+
–
hyphae (n)
fused hyphae (n + n)
fusion of nuclei(karyogamy)
meiosis of “zygote-like” structures
dispersal of spores
zygote (2n)
sexual spores (n)
+
–+
–
Sexual reproduction in fungi
Haploid spores may disperse long distances away from the fruiting body
Key
Plasmogamy
Karyogamy
Meiosis
Black Bread Mold
Sexual reproduction
Asexualreproduction
Mating type (+)Mating type (-)
Zygosporangium
Haploid (1n)Heterokaryotic (1n + 1n)Diploid (2n)
Fungal Life Cycles
Key
Haploid (n)
Heterokaryotic
Diploid (2n)
PLASMOGAMY(fusion of cytoplasm)
Heterokaryoticstage
KARYOGAMY(fusion of nuclei)
SEXUALREPRODUCTION
Spore-producingstructures
SporesASEXUALREPRODUCTION
Zygote
Mycelium
GERMINATION GERMINATION
MEIOSIS
Spore-producingstructures
Spores
Fusion of compatible hyphae (plasmogamy)
Fungal Life Cycles
Key
Haploid (n)
Heterokaryotic
Diploid (2n)
PLASMOGAMY(fusion of cytoplasm)
Heterokaryoticstage
KARYOGAMY(fusion of nuclei)
SEXUALREPRODUCTION
Spore-producingstructures
SporesASEXUALREPRODUCTION
Zygote
Mycelium
GERMINATION GERMINATION
MEIOSIS
Spore-producingstructures
Spores
Fusion of compatible hyphae (plasmogamy)
…initiates a heterokaryotic phase
Fungal Life Cycles
Key
Haploid (n)
Heterokaryotic
Diploid (2n)
PLASMOGAMY(fusion of cytoplasm)
Heterokaryoticstage
KARYOGAMY(fusion of nuclei)
SEXUALREPRODUCTION
Spore-producingstructures
SporesASEXUALREPRODUCTION
Zygote
Mycelium
GERMINATION GERMINATION
MEIOSIS
Spore-producingstructures
Spores
Fusion of nuclei (karyogamy)
Fungal Life Cycles
Key
Haploid (n)
Heterokaryotic
Diploid (2n)
PLASMOGAMY(fusion of cytoplasm)
Heterokaryoticstage
KARYOGAMY(fusion of nuclei)
SEXUALREPRODUCTION
Spore-producingstructures
SporesASEXUALREPRODUCTION
Zygote
Mycelium
GERMINATION GERMINATION
MEIOSIS
Spore-producingstructures
Spores
Fusion of nuclei (karyogamy)
…initiates a zygotic phase
Fungal Life Cycles
Key
Haploid (n)
Heterokaryotic
Diploid (2n)
PLASMOGAMY(fusion of cytoplasm)
Heterokaryoticstage
KARYOGAMY(fusion of nuclei)
SEXUALREPRODUCTION
Spore-producingstructures
SporesASEXUALREPRODUCTION
Zygote
Mycelium
GERMINATION GERMINATION
MEIOSIS
Spore-producingstructures
Spores
Fusion of nuclei (karyogamy)
…initiates a zygotic phase
…which is perhaps best described as “zygote like”
Fungal Life Cycles
Key
Haploid (n)
Heterokaryotic
Diploid (2n)
PLASMOGAMY(fusion of cytoplasm)
Heterokaryoticstage
KARYOGAMY(fusion of nuclei)
SEXUALREPRODUCTION
Spore-producingstructures
SporesASEXUALREPRODUCTION
Zygote
Mycelium
GERMINATION GERMINATION
MEIOSIS
Spore-producingstructures
Spores
Meiosis in “zygote-like” cells produces spores or cells that will produce spores
Fungal Life Cycles
Key
Haploid (n)
Heterokaryotic
Diploid (2n)
PLASMOGAMY(fusion of cytoplasm)
Heterokaryoticstage
KARYOGAMY(fusion of nuclei)
SEXUALREPRODUCTION
Spore-producingstructures
SporesASEXUALREPRODUCTION
Zygote
Mycelium
GERMINATION GERMINATION
MEIOSIS
Spore-producingstructures
Spores
Both asexual & sexual reproduction produce
haploid spores
Kind of Asexual Spores• Arthrospore – spore formed by
fragmentation of the tip of the hyphae
• Blastospore – produced as an outgrowth along a septate hypha.
• Conidiospores – unprotected spores formed by mitosis at the tips of the hyphae
• Sporangiospores – spores produced within a sac called sporangium
Sexual reproduction in a chytrid:flagellated spores
spores
Other forms of Reproduction
• Budding
• Occurs in yeasts when it undergoes mitosis and forms a tiny cell at its border
• The cell produced increases in size and eventually separates from the parent cell
Budding Yeast
Body Plan• unicellular (yeast), filamentous, or both (=dimorphic)
• Hypha (pl. hyphae) is the basic “cellular” unit in filamentous fungi; they may be septate or coenocytic (aseptate); collectively a mycelium
• limited tissue differentiation and division of labor
• somatic & reproductive structures
• plectenchyma: all organized fungal tissue, somatic & reproductive
Nuclear Status• Eukaryotic; uni, bi- or multinucleate• Haploid, diploid (less frequent)• Monokaryon (1 nucleus per hyphal compartment)
• Dikaryon (2 nuclei per hyphal compartment) • Homokaryotic
• Heterokaryotic
• Mitosis– intranuclear: nuclear membrane doesn't
breakdown during mitosis– centric in flagellated forms; typical centrioles
of eukaryotes– noncentric in nonflagellated forms; possess
spindle pole bodies (SPBs); differ from centrioles in lacking microtubular component
Organelles• typical eukaryote assemblage of organelles
+ fungal specific ones• mitochondria • endoplasmic reticulum • Golgi equivalents
single cisternal elements • vacuoles • microbodies
function in fatty acid degradation, Nitrogen metabolism
Cell Wall• well defined
• chitin
1-4 n-acetyal glucosamine -glucans
polymers of glucose
1-3 glucose
• cellulose in some
1-4 glucose
chitin -glucans
Chitin
Cellulose
1-3 glucan
•fungal specific organelles involved in cell wall growth
Spitzenkorper
associated with growing hyphal tips in septate fungi
chitosome
microvesicles transporting chitin synthases to growing cell wall
Uses of Fungi
As Biotic control agents
The first antibiotic used by humans
Staphylococcus
Penicillium
Zone of inhibited growth
Uses/Functions of Fungi
Biotic control agents
Used against termites, rice weevils, etc.
Uses/Functions of Fungi
Interesting example…
of agriculture in insects
Leaf-cutter ants cut and carry leaf fragments to their nests where the fragments are used to farm fungi
Uses/Functions of Fungi
Interesting example… of fungal cowboys
Some soil fungisnare nematodeworms in hyphalnooses and thendigest them
unlucky nematode
fungal hypha
Functions/Uses of Fungi
Interesting example… of fungi & conservation
The golden toad became extinct within the past 20 years, owing to anthropogenicenvironmental deterioration,which also facilitated pathogenic chytrid fungi
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