Introductory Mycology

CHARICTERISTICS

75,000 species have been described 1.5 million are believed to exist Eukaryotes originally characterized as plants

Heterotrophic, not autotrophic; Lack chlorophyll Cell walls made of chitin, not cellulose

Spores – Microscopic disseminating cells for germination over distance

CHEMOHETEROTROPHS

Chemoheterotrophs - Secrete enzymes to hydrolyze and absorb preformed surrounding organic matter

Saprobes – decomposers of dead/decaying organic matter Opportunistic – cause disease in immunocompromised

CHITIN

Cells are housed in... Chitin cell wall composed of acetylglucosamine Provides rigidity as well as strength Do not suffer hydrolysis under water pressure Adapted to survive in moist environments

DIMORPHISM

Yeasts – unicellular, resemble bacteria on substrate plates

Vs. Molds – long tangled filamentous cells give rise to viable

colonies Dimorphic – form varies with temperature, frequent in

pathogens unicellular at body temp 25oC filamentous molds – ambient temperature 37oC unicellular pathogenic bacillusesque – body

temperature

MOLDS Hyphae- intertwined tubular filaments morphological unit Mycelium – thick mass visible to the naked eye, feeding

network for absorption Filamentous fungi form a network of hyphae called a

colony. Aspergillus niger forms cm-scale macro-colonies on a solid

surface and (sub)-mm-scale micro-colonies in liquid cultures.

HYPHAE

long, branching filamentous structure hyphae are divided into cells by internal cross-walls

called septa Mycelial growth caused by hyphae elongation - cell walls

are extended by the external assembly and polymerization of cell wall components, and the internal production of new cell membrane

Vesicle membranes contribute to growth of the cell membrane while their contents form new cell wall. The spitzenkörper moves along the apex of the hyphal strand and generates apical growth and branching

SEPTAE

• Divide cytoplasm, possibly porous to the extent that ribosomes can pass through• As seen in Penicillium chrysogenum• No pores in Rhizopus

• Coenocytic – no septa

PERMIAN EXTINCTION• 250 million years ago the Permian Extinction decimated 96% of oceanic

species• associated with a sharp increase in the abundance of marine and terrestrial 

fungi, caused by the sharp increase in the amount of dead plants and animals fed upon by the fungi

• For a while this "fungal spike" was used by some paleontologists to identify the Permian–Triassic boundary in rocks that are unsuitable for radiometric dating

GROWTH SPECIFICATIONS

• Majority aerobic – exception facultative yeast• Temp 23C

WHY FUNGI?

•Pathogenic – kept at bay by CD8+ T-cells, but concern for immunocompromised patients (AIDS)

•Many medicines come from fungi, such as penicillin, statins, and many ancient Eastern medicinals