Week 7: Fungi

general characteristics of Kingdom Fungi

contains more than 81,000 known species (most are terrestrial), all are eukaryotes, not all are multicellular, contain the largest known organism on earth

what characteristics do all fungi share?

they are heterotrophs that absorb nutrients, they have multicellular and unicellular forms, they have cell walls that include chitin, some have a dikaryon stage

what is the general biology of fungi?

multicellular forms consist of long, slender filaments called hyphae. a mass of connected hyphae is called a mycelium (grows through and digests its substrate - external digestion)

monokaryotic

one nucleus

dikaryotic

two nuclei

coenocytic

no cross-walls, multinucleated hyphae

how are hyphae divided?

they are divided into compartments by septa

how do fungi obtain food?

they secrete digestive enzymes into their substrates. they then absorb the organic molecules produced by this external digestion. they can break down cellulose and lignin. some are carnivorous

what are the six main groups of fungi?

microsporidia, chytrids, zygomycetes, glomeromycetes, ascomycetes, basidiomycetes

how do fungi primarily reproduce?

via spores, both sexually and asexually

what is fungal classification based on?

the mode of sexual reproduction

characteristics of microsporidia

microscopic spore producers, grouped with fungi based on genetic investigation, are obligate intracellular parasites, mitochondria are replaced with mitosomes, produce sexual and asexual spores and contain chitin in their cell walls

characteristics of chytridiomycota

aka chytrids, most closely related with ancestral fungi, only fungi with flagellated spores, have chitin in their cells walls, life cycle has both haploid and diploid multicellular stages

characteristics of zygomycetes

include the common bread molds and a few human pathogens, the hyphae are coenocytic except for when they are reproducing

characteristics of glomeromycota

a tiny group of monophyletic fungi, they form intracellular associations with plant roots called arbuscular mycorrhizae, show no evidence of sexual reproduction

what is the ecological importance of mycorrhizae?

mycorrhizal fungus decompose organic material in the soil, benefit plants by increasing their absorptive surface area, roots supply fungus with sugars, amino acids, and other organic substances, scientists have measured the movement of organic materials from one tree species to another

characteristics of phylum ascomycota

sexual spores are produced in a sack called an ascus, hyphae usually have septa, but the cytoplasm is continuous

include most yeasts, powdery mildews, morels and truffles, dutch elm disease, ergot disease on rye, moldy cheese

what are examples of asexual ascomycetes?

economically important molds such as penicillium (penicillin, blue cheeses), and aspergillus (soy sauce, soy paste)

what is the life cycle of a typical ascomycete?

gametangia fuse, forming dikaryotic hyphae, asci develop from dikaryotic hyphae, asci are incorporated into an ascocarp

characteristics of phylum basidiomycota

the two mating types fuse and form dikaryotic hyphae, develop basidia, each basidium is an enlarged hyphal cell, four basidiospores develop on the tip of the basidium. include mushrooms and puffballs

characteristics of lichen

dual organism: symbiotic association between a phototroph and a fungus

phototrophic component is either a green alga or a cyanobacterium

fungus is an ascomycete (or occasionally a basidiomycete)

what are the three growth forms of lichen?

crustose (“encrusted” on plant, very low-growing layer)

foliose (“foliage” appearance, leaf-like)

fruticose (branch-like)

how do lichen reproduce mostly?

asexually

how can lichen indicate environmental quality?

they are very sensitive to atmospheric changes (ex. nitrogen or heavy metals)

what is the ecological significance of lichen as decomposers?

they absorb nutrients from organic wastes, they release water, CO2 and mineral components of organic compounds, which are recycled

what are some economic and medical uses of fungi?

in beverages (alcoholic beverages), food, medicine, chemicals

what are examples of fungal parasites and pathogens?

molds, smuts, rusts, mildews, and rot

ringworm and athlete’s foot, sick building syndrome

characteristics of cordocytes

ascomycetes, some cause zombie ants, some are beneficial to human health (help increase oxygen uptake in the body)

what is massospora?

a zygomycete that infects periodical cicadas (every 13 or 17 years), fungus replaces parts of the abdomen with a mass of spores, becomes hypersexual

what is mucormycosis?

a zygomycete - causes infection and sometimes necrosis