BIOL 2004 Lecture Notes - Lecture 10: Actinobacteria, Osmotrophy, Ethanol Fermentation
3 May 2018
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Fungi
April 5, 2016
• Very diverse group: ~100,000 described species
• Some small and unicellular, some have large fruiting bodies (ex. Mushroom)
o Large and complex = multicellular or coenocytic
• Opisthokonts = closely related to animals and choanoflagellates
• Non-phagotrophic: typically saprotrophs
• Most are terrestrial
o Important in decomposition
o Many parasitic
o Many beneficial symbionts
• Can encompass a large area; most of fungus is subterrerean
Nutrition and Metabolism:
• Saprotrophs – absorptive nutrition
o Secrete digestive (exo)enzymes
o Absorb dissolved nutrients by osmotrophy
• May be simple osmotrophs = feed on substances already in form of simple sugars (like on
fruit)
• Most are aerobic but some anaerobes (e.g. ethanol fermentation in yeast)
Generalities:
• Immotile: non-flagellated (except spores and gametes of chytrids)
• Most are filamentous with hyphae
o Mass of hyphae = mycelium
• With cell wall predominantly consisting of polysaccharide (chitin)
o Resistance to water stress; physical protection
o Strength: supports penetration into material or hosts (rigid tube)
o Crucial to how fungi exploit their environments
• Reproduction
o Asexual: especially by asexual spores
o Sexual: reproductive structures produce sexual spores
Hyphae
• Branching filaments (typically few um across)
• Rapid growth
• Can rapidly penetrate surrounding environment
• Filamentous form gives very high surface area: volume ration nutrient absorption
*important for osmotrophs (site of nutrient uptake is at cell membrane)
“fungi are eukaryotes pretending to be prokaryotes” = similar to actinobacterium (contain
mycelium) convergent evolution
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Document Summary
April 5, 2016: very diverse group: ~100,000 described species, some small and unicellular, some have large fruiting bodies (ex. Hyphae: branching filaments (typically few um across, rapid growth, can rapidly penetrate surrounding environment, filamentous form gives very high surface area: volume ration nutrient absorption. *important for osmotrophs (site of nutrient uptake is at cell membrane) Fungi are eukaryotes pretending to be prokaryotes = similar to actinobacterium (contain mycelium) convergent evolution. The growing hyphal tip: role of tip is to elongate, absorption zone apical growth zone (contains secretory vesicles = exocytosis for growth and to generate more materials for growth) *powered by turgor (water pressure) Coenocytic hyphae: generate new nuclei via mitosis. Septate hyphae: septa block movement of larger organelles (especially nuclei, continuous cytoplasmic communication between cells through pores in septate wall. Yeast: are not hyphal at some part in lifecycle, unicellular form of fungi that has evolved several times, most reproduce sexually by budding.
