Lecture 20: Fungal Physiology and Life Cycles

animals and plants closely associated, branch off from fungi. Eukaryotes “any of a group of spore-producing organisms feeding on organic matter, including moulds, yeast, mushrooms, and toadstools.”

animals and plants closely associated, branch off from fungi. Eukaryotes “any of a group of spore-producing organisms feeding on organic matter, including moulds, yeast, mushrooms, and toadstools.”

• Unique lysine synthesis method • AAA pathway • AminoAdipic Acid pathway • Animals = DAP pathway • Ridged cell wall composed of beta-1,3 and beta-1,6 linked glucans, mannan and chitin • Cell membranes contain “ergosterol” (animals have cholesterol, plants have sitosterol) - OFTEN A TARGET FOR TREATING FUNGAL INFECTIONS

• Basidiomycota a. Most mushrooms, other macroscopic fungi in this group • Ascomycota a. Industrially important b. e.g., penicillium (prod penicillin) c. e.g., aspergillus (prod of chemicals) d. Some macroscopic, most moulds • Glomeromycota a. New phylum b. Mycorrhizal fungi c. Important symbiotic relationship with plants • Zygomycota a. Pin-head fungi • Chytridiomycota a. water fungi b. Mostly saprotrophs, some pathogen c. Batrachochytrium dendrobatidis = causes chytridiomycosis

1. Most fungi are filamentous, made of "tubular", thread-like "hyphae" 2. Mass of hyphae is termed "mycelium" 3. Sometimes large macroscopic bodies are produced 4. Some fungi unicellular

• growth occurs at tips of hyphae

• Made of a thin transparent tubular cell filled or lined with protoplasm. a. Diameter: 1-30um • Hyphae are colourless (hyaline), fungal colonies are coloured due to pigmentation in spores • Tapered at the tip, called “extension zone”

Hyphae everywhere. Make up the fibrous “body”/structure Reproductive structure: The head of the mushroom - spores located underneath the lip Reproductive structures produces when moist and not too hot (autumn)

Hyphae everywhere. Make up the fibrous “body”/structure Reproductive structure: The head of the mushroom - spores located underneath the lip Reproductive structures produces when moist and not too hot (autumn)

• Determine the shape of the fungus • Act as an interface between the fungus and its environment • Protect against osmotic lysis, regulates passage of large molecules • Antigenic properties that can mediate with the other organisms

• 80-90% polysaccharides • The chytridiomycota, ascomycota and basidiomycota have “chitin”. • Zygomycota have mixture of “chitin” and “chitosan” Chitin - polymer of N-acetylglucosamine a. also found in insect exoskeletons Chitosan - polymer of D-glucosamine a. deacetylated form of N- acetylglucosamine

Four zones • Amorphous glucans • glycoprotein + protein • Protein • Chitin + protein • Plasma membrane

1. In most species; hyphae are interrupted by cross-wall called "septa" 2. Septa are usually perforated - allowing passage of cytoplasm, and even nuclei between parts of hyphae 3. May act as structural report 4. May be first line of defence against damage “SIMPLE” = septum has large central pole (Ascomycota) “DOLIPORE” = septum (Basidiomycota), narrow central pole, flanked by bracket-shaped membranes called “PARENTHOSOMES” (clamp connections) a. does not allow passage of nuclei, ensures dikaryotic condition

• Form just behind each septum • Proteinaceous lattices surrounded by a membrane • Plug the sepal pores if the hyphae are damage, becoming old or undergoing differentiation

• Dimorphism • Development of structures involved in sexual reproduction

• Can change between yeast and mycelial form • Common for animal and human fungus pathogens: a. filamentous outside host b. single cell inside the host • change from filamentous to yeast form can be bought about by changing the environmental conditions (e.g., oxygen, sugar, calcium concentrations) E.G., Candida albicans grows as a yeast in moist mucosal membranes of humans, but converts to hyphal to invade tissues

1. Fungal hyphae extend continuously at extreme tips 2. Growth supported by continuous movement of mineral into the tip from the older regions of hyphae 3. Hyphae are a continuous movement of protoplasm, which thrusts the growing tip forward

• Growing tip of hyphae contains very few organelles, instead contains a body called “spitzenkorper” (apical body) • This consists of a cluster of small, membrane bound vesicles embedded in a meshwork of actin microfilaments • Its always present in growing tips, disappears when growth stops and reappears if growth restarts

1. Small organic food molecules transported across plasma membrane 2. Polymeric food molecules must be depolymerised 3. Depolymerizing enzymes are secreted by vesicles fusing with the membrane

• Sexual reproduction • Asexual reproduction Spores are essential for this.

• Germination • Mycelium (n) • Spore producing structures (n) • Spores (n) • Repeat

• Dikaryotic stage (n+n) • Karyogamy (function of nuclei) • Diploid stage (2n) • Meiosis • Spore producing structures (n) • Spores (n) • Germination • Mycelium (n) • Plasmogamy (fusion of cytoplasm) • repeat

• Fungal mating types are determined by: “mating-type locus” • Different mating types of fungi look the same.

1. To extend beyond the existing environment a. escape nutrient depletion b. Exploit new potential environmental niches