FUNGAL BIODIVERSITY

CHARACTERISTICS OF FUNGIStructure

eukaryotic- individual cells are typically larger and more complex than bacterial cellsDimorphic - unicellular (yeasts) or multicellular (molds ... mycelium that is a mesh of elongated filamentous hyphae that are frequently branched, with perforated septa between cells to ensure unimpeded movement of nutrients from one region of the mycelium to another) ... some fungi are dimorphic (change back and forth from yeast to mold)Chitin in cell walls of most, but some contain cellulose instead; protect the cytoplasm from osmotic pressure changes and provides cell shapeMembranes- glycerol-based phospholipids with ester linkages which form typical bilayer membranesRibosomes - 80S RNA/protein particles which are required for protein synthesis

Genetics chromosome - multiple, non-identical DNA molecules

complexed with histones; the DNA contains the "blueprint" for all cell structure and activity in regions called genes

introns and exons are present in fungi, as they are in the typical eukaryote

gene exchange - recombination during meiosis generates diversity

Reproduction - generally via modified hyphae that form reproductive spores sexual - fusion of haploid nuclei leading to formation of spores asexual

binary fission budding - unequal binary fission fragmentation of hyphal elements

arthrospores formed directly from hyphal fragmentation chlaymdospores formed from directly hyphal fragmentation,

but surrounded by a thick wall Spores - thick walls help them withstand dry, cold, low-nutrient

conditions

Physiology aerobic (some facultatively anaerobic, but none are anaerobic) organotrophs absorptive nutrient uptake- these cells secrete digestive enzymes to break down

macromolecules to their subunits, then internalize the subunits to derive energy and structural building blocks

most are mesophilic (20-35C optima); some are psychrophilic, some are mildly thermophilic

pH optimum near 5.5, but some grow at extremes of the pH range 2-9

Habitat - generally prefer dark, moist habitats containing organic material terrestrial or aquatic (some live in freshwater, others in marine, habitats) symbiotes with plants (mycorrhizae) or algae or cyanobacteria (lichens)

Importance most saprophytic (decomposers); some are pathogenic for plants or animals some are symbiotic, especially those that are the fungal component of lichens important commercially in food production and spoilage, as well as pharmaceutical

and industrual chemical production

Groups of Fungi (~100,000 species)

Chytridiomycota - Chytridiomycetes or Chytrids morphology - globe-shaped cells with rhizoids

Reproduction

habitat/importance saprophytic decomposers which grow in on decaying plants or animals,

mainly in freshwater habitats (including mud) parasitic - some infect living plants, animals and other fungi

Zygomycota - Zygomycetes, zygosporangium-forming fungi (~600 species)Morphology - mycelial

Habitat/importancegenerally saprophytic decomposers in soil, important in plant

decayRhizopus stolonifer (common bread mold) is

used commercially to produce tempeh (from tofu), pharmaceuticals including anaesthetics, contraceptives, industrial alcohols, meat tenderizer, yellow dye for margarine

Ascomycota- Ascomycetes, sac fungi (~35,000 species)Morphology - dimorphic (yeast or mycelium with septate hyphae)

Habitat/importance - generally saprophytic decomposers in soil, but some are used for food and some are parasitic• helpful - Morchella esculenta (morels) and Tuber brumale

(truffles) are edible; Saccharomyces (cerevisiae, carlsbergensis, ellipsoideus) used to make bread, beer, wine; Neurospora crassa genetics research tool (spoilage-inducing bread mold)

• damaging (parasites, etc.) - Claviceps purpurea causes ergot of rye; 

Basidiomycota - Basidiomycetes, club fungi, aka mushrooms (~30,000 species) morphology - dimorphic (yeast or mycelium with septate hyphae and fruiting bodies

we recognize as mushrooms, shelf fungi, puffballs, etc.) reproduction

sexual spores are basidiospores - formed by the basidium (club-shaped structure at tip of hyphae; may be inside a fruiting body called a basidiocarp)

asexual reproduction - budding, fragmentation of the mycelium, and by production of conidiospores, arthrospores, or oidia (Coprinus lagopus)

habitat/importance - generally saprophytic decomposers in soil, but some are used for food and some are parasitic

helpful - Agaricus campestris bisporus is an edible mushroom damaging (parasites, etc.) - Amanita phalloides is poisonous (produces phalloidin

and alpha-amanitin); Cryptococcus neoformans, human pathogen; Puccinia graminis causes black stem wheat rust; Ustilago maydis - causes corn smut

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