Components of wood:
Cellulose (C6 H10 O5):
A polysaccharide consisting of a linear chain of several hundred to many thousands of Beta linked D-glucose units. It is the most abundant organic polymer on Earth.
Hemicellulose: A polysaccharide comprising about 20% of the biomass of most plants. Derived from several sugars in addition to glucose. Consists of shorter branched chains.
Lignin: Cross-linked phenolic polymers important in the formation of cell walls, especially in wood and bark because they lend rigidity and do not breakdown easily.
Brown rot fungi
Capable of breaking down cellulose and hemicellulose but leave lignin behind. This type of decay most common in conifers.
White rot fungi
Break down cellulose, hemicellulose and lignin. Common in all types of trees.
Peat
Partially decayed plant material. Serves as a carbon sink. When plants died, their bodies formed peat.
Peat acidified the swamps and reduced fungal abundance.
How can a fungus take apart a tree
- The fungal body is a mycelium and it consists of a group of hyphae
- Hyphae have a high surface area to volume ratio. Most cells are directly in contact with the environment.
- Extracellular enzymes are synthesized inside hyphae and then secreted to the outside.
- The products of extracellular digestion are absorbed across the hyphal wall. They have absorptive nutrition (absorptive heterotrophs).
As substrates for fungal growth, lignin and methane are:
-Rarely used - about as rarely used as Keratin in hair.
Easy substrates include:
Fruit, flesh, leaves, cotton, and paper. Wood, bone, nails, hair, paint, cosmetics, soaps, leather, and fuel are more difficult.
Saprobes (decomposers)
Break down dead organic matter and are essential for nutrient cycling
Composting
Driven by saprobic fungi, the metabolism of which can be very hot.
Mycorrhizae
Ancient symbioses with Embryophytes that involve several lineages of fungi
Benefits:
- Protection from root pathogens
- Increased longevity of fine roots
- Protection from heavy metals in soil
- Linkages between plants
Microsporidia
- Intracellular parasites
- Infect arthropods, vertebrates
- No mitochondria
- Spores invade cells and allow for dormancy outside of a host
Cryptomycota
A recently discovered lineage of fungi. They are small and form close associations with many organisms.
- Only detected through genomic analyses.
- They attach to, engulf, or live in other cells and feed by phagocytosis.
- Lack chitin in the cell walls of their feeding stages
Chitin
a fibrous substance consisting of polysaccharides and forming the major constituent in the exoskeleton of arthropods and the cell walls of fungi.
Chytrids
- Non-monophyletic group
- Swimming spores and gametes
- Swimming spores have been lost in other fungal lineages
- Coenocytic diploid stage goes through meiosis to produce haploid spores which make a haploid multicellular gametophyte.
Key feature of Dikarya (Synapomorphy)
The presence of a dikaryon which has a ploidy of n+n
- Two genetically distinct haploid nuclei in each cell
- Individual cells do not act as gametes
- Hyphal fusion with nuclei acting as gametes
- No real gametic stage.
Ascomycota
Largest group of fungi
- Diagnostic spore structure - Ascus
- Cup like fruiting bodies
- Sexual or asexual reproduction
- Many yeasts and molds are ascomycetes
- There are meiospores and mitospores
Fruiting bodies have variety of shapes: including edibles like morels and truffles.
Mold
Ascomycetes that lack sexual reproduction in their life cycle. Does not include slime mold.
Conidia
Mitospores produced via mitosis (asexually). They form by pinching off cells at tips of hyphae.
Basidiomycota
2nd largest group of fungi
- Diagnostic spore structure - Basidium
- Fruiting bodies are variable, but many look like typical mushrooms.
Yeast
Unicellular fungi; Chemoorganotrophs.
Lichens
Symbiosis formed between Ascomycota and algae or cyanobacteria
-Body formed from fungal hyphae. Nearly all of them are obligately dependent on their photobiont
Symbiosis
Nearly all photobionts are not obligately depndent on the lichen
Mycotoxins
Secreted by fungi and may have important impacts on human health; either through secondary infection or chronic exposure
Principle of continuity
Reducing the cross-sectional area of an outflow results in increased velocity
