Introduction To Fungi Flashcards
Opistokonta
Large supergroup of eukaryotes including metazoans and fungi
-phagotrophic or osmotic (saprophytic, parasitic). Some symbiotic with land plants
-flagellate cells possesses various types and numbers of flagella inserted posteriorly
Saprophytic
Breaking down dead organic materials
Diversity of fungi
80,000-120,000 described, estimated 1.5M
-least explored bio diverse group
Diversity of fungi trend
-typically warm and moist climates
-distance from equator and mean annual precipitation had strongest effect of fungi diversity
-ectomycorrhizal fungi most common in boreal and temperate ecosystems (trees)
-however, not fully correct as too much area was extrapolated
What things define fungi
-nutrition
-vegetative state
-cell wall
-nuclear status
-propagules
-habitat
-ecology
-distribution
-heterotrophic
-non-motile mycelium of hyphae
-glucans and chitin
-eukaryotic, uni or multi nucleate
-microscopic spores produced in high numbers
-terrestrial, fresh water and marine
-saprotrophs, mutualistic symbionts, parasites
-wide
Hyphae distinguished by…
Distinguished by reserve of absence of cross walls (septa)
-oomycota and zygomycota: generally aseptate hyphae, coencytic
-ascomycota and basidiomycota: septate hyphae where each segment contains 1,2 or more nuclei
Growth forms of fungi
Aseptate hypha (zygomycota)
Septate branched hypha (ascomycota)
Yeast cells dividing by binary fission (ascomycota)
Yeast cells dividing by budding (basidiomycota)
Pseudohypha (ascomycota)
Lower fungi grow as a _____
Thallus: walled structure where protoplasm is concentrated in one or more centres from which root-like branches (rhizoids) grow
Obligately plant-pathogenic fungi and fungus-like organisms may grow as a naked ______
Plasmodium: uni or multi nucleate mass of protoplasm not surrounded by a cell wall of its own
What is the most unique group of fungi?
Oomycota
-no chitin, but had cellulose
Fungi reproduction
Small, asexual spores produced in large numbers
Zoospores with various types and numbers of flagella
Single hypha produced by fusion typically have ______ nucleus per “cell”, and it known as ______
2
Dikaryon
_______ may live and grow for years, and some are thought to be centuries old
Dikaryon
Fungi feed by ______
Absorption of nutrients from the environment around them. Hyphae secrete digestive enzymes which break down the substrate.
Uptake in fungi is mediated by proteinaceous pores in plasma membrane: channels or porters
Channels
Porters
Facilitate diffusion of solutes following concentration gradient (high concentration)
Use metabolic energy (H+ gradient) to accumulate the solute across the plasma membrane against its gradient (low concentration)
1/3 of total cellular ATP used to establish ________
Transmembrane H+ gradient
Uni port and symport carriers
Couple the inward movement of H+ with the uptake of uncharged or negatively charged solutes
Antiports
Harness the outward diffusion of cations such as K+ for the uptake of other positively charged solutes
Hyphae growth
-growth nearly infinitely by extension at their tips
-can reach a length of several kilometres
________ events aggregate groups of hyphae leading to synchronized growth
_________ may influence gene expression between adjacent hyphae
Signalling
Secretion of chemical messengers
Cytoskeleton in fungi
Microtubules involved in long-distance transport of organelles: secretory vesicles, nuclei, and positioning of mitochondria, nuclei or vacuoles
Also include actin filaments
Proposed mechanism of hyphae growth
Cytoskeleton is probably responsible for pushing the hyphal tip forward
Stretch-activated Ca2+ channels concentrated in apical plasma membrane
Stretched plasma membrane admits Ca2+ ions to contact actin cap= reduce apical growth
Sequestration of Ca2+ by subapical vacuoles lowers Ca2+ resulting in relaxation of actin cap and hyphal growth
Scaffold model of growing hyphae
-secretory vesicles and chitosomes (synthesize chitin) transported along microtubules from their subapical sites of synthesis
-apical body (spitzenkorper) forms around a cluster of actin filaments
-actin scaffold inside apex is linked to rivet-like integrin molecules
-apex further stabilized by spectrin molecules longing the cytoplasmic surface of the plasma membrane
Formation of aggregates of parallel, relatively undifferentiated hyphae is coming in ______ and some _____
Basidiomycota
Ascomycota
Mycelia’s strands form a ______of the cultivated mushroom agaricus Bosporus
Spawn
Fungi evolved when
> 900 mya
Estimate is consistent with the discovery of fossilized hypha-like structures in sediments about 1bya
Are fungi good fossils?
No
Often found within plant fossils with symbiotic relationship to fungi
Two main theories on the evolution of fungi
- Old theory that fungi evolved from algae that lost chlorophyll. Green algae evolved into power fungi and red algae became ascomycota
- Animals and fungi are closer in relation than either are to plants-both have origins to opisthokonta
Earliest branching lineage of fungi
Chrytids
