Fungus
Kingdom Fungi:
Mycology: study of Fungi
Appeared about 400 mya
Not plants or animal
True multicellular with different types of cells
Strictly heterotrophic
Release digestive enzymes into environment that break down matter in their environment: extra cellular digestion
Some can digest dead organisms: decomposers
Some parasitic: feeding on living organisms and causing disease
Some predatory: can attack small worms in soil
Most saprophytic: decompose nonliving organic matter
Ex: yeast flour
In forests: leaves and animal waste
Along with bacteria, fungi are an important decomposer
Some decompose living tissue
Eg: athletes foot and ringworm
We use fungi to produce food and medicine
Biology of Fungi:
Body of fungus is mass of filaments called a mycelium
Each filament is a hypha
Hyphae allow organism to increase surface area in order to maximize contact with ground
Some have cross walls between cells called septa
Have pores that allow fungal cells to exchanges components of cytoplasm
Non septate fungi lack cross walls between cells: multinucleate
s
Fungal cell structure:
Cell wall contains chitin instead of cellulose
Energy reserve is glycogen like in animal cells
Nonmotile
Move toward food source by growing towards it
Absorption heterotrophs: absorb nutrients from environment
Exhibit nuclear mitosis
Different from other eukaryotes
Chromosomes dragged to opposite poles by spindles inside nucleus
Process creates 2 cells
Fungal reproduction
Adapted to dry land
Product windblown spores
Spore: reproductive cell or multicellular structure that is resistant to environmental conditions and can develop into an adult without fusion with another cell
Haploid reproductive cell germinates and develops into new mycelium (asexual reproduction)
Sexual reproduction occurs by conjugation of 2 different mating types
Genetically different nuclei
Designated by + and -
After fusion of nuclei a zygote forms
Zygote undergoes meiosis
Produce haploid spores and cycle begins again
Fungi classified on basis of sexual structures
Phylum Zygomycota
Zygospore fungi
Saprotrophs and parasites
Eg: Rhizopus stolonifer: black bread mold
Phylum Ascomycota
Sac fungi
Sexual reproductive structure called ascocarp
Many sac fungi reproduce by producing chains of spores: conidia
Ex: disease causing sac fungi
Chestnut blight, dutch elm disease, Ergot
Candida causes thrush in humans
Some sac fungi useful to humans
Original source of penicillin
Used to produce blue cheese
Yeasts single celled fungi used in food industry
Morels and truffles
Phylum Basidiomycota
Club fungi
Ex: mushrooms, shelf fungi and puffballs
Structure includes stalk and cap with gills
Spores located in gills
Few edible species
Many toxic to humans
Rusts and smuts cause disease in plants and become a serious threat to food supply
Characteristic sexual reproductive structure: basidium
Contained within a basidiocarp
Edible part of a mushroom is basidiocarp
Located in gills of cap
Forms after fusion of + and - hyphae
Sexual reproduction is most common in this group
Asexual reproduction can occur by asexual spores
Lichens
Symbiotic relationship between fungi and cyanobacteria or green algae
Efficient at acquiring nutrients and moisture
Can colonize poor soil and rocky surfaces
Produce organic matter and create new soil
3 characteristic forms
Crustose (compact)
Foliose (shrub like)
Fruticose (leaf like
Body has 3 layers: fungi form top and bottom layers and protect middle layer of photosynthetic cells
Fungi portion offers protection and delivers water
Photosynthesis gives nutrients
Mycorrhizal fungi
Mutualistic relationship with plant roots
Help plants grow more successfully in poor soils
Fungi can live on outside surface of roots or can penetrate root tissues
Plant provides nutrients to fungus
Fungus bring water and minerals to plant
Hyphae provide lots of surface area for water absorption
Fungal disease of plants
Many enter through stomata of leaves or through a wound
Smuts and rusts: sac fungi that parasitize cereal crops
Fungal Disease of Humans (mycosis)
Athlete’s foot
ringworm
redness (inflammation due to enzymes released by fungus); extends outward in ring shape
Candidiasis (Candida albicans)
Yeast infection resulting from imbalance of normal flora
Histoplasmosis (Histoplasmosis capsulatum)
Can be transmitted by bird droppings
May be asymptomatic or mild flu like symptoms
In more serious cases: lesions may form in lungs which later become calcified
Control of Fungi:
Fungi more closely resemble animal cells than bacteria
Makes it harder to develop antibiotics that will kill fungi and not the host
Fungi synthesizes steroids differently
Fungicides are directed at steroid biosynthesis