Nutrition, structural organization, growth and reproduction distinguish group organisms in the other four kingdoms.
A. Nutrition
Fungi secrete hydrolytic enzymes and acids in order to breakdown and absorb organic molecules.
- Saprophytes, parasitic fungi, and mutualistic fungi
- terrestrial, aquatic and symbiotic relationships with algae and cyanobacteria to form lichen.
B. Structure - form mycelium (vegetative body) - intertwining mats of hyphae that are organized around and within their food source.
-cell walls contain chitin
- mycelium provides tremendous surface area
- Parasitic fungi have haustoria - that are modified hyphae which penetrate host tissue.
aseptate - fungi lack cell walls and are coenocytic.
septate - fungi are divided into cells by crosswalls called septa.
No flagellated stages in their life cycle.
C. Growth and Reproduction
Nonmotile, grow in length not girth, as much as a kilometer a day.
During mitosis the nuclear envelop is in tact and spindle is inside nucleus.
Fungi reproduce by producing spores that are haploid and of different shapes and sizes. These are produced either sexually (meiosis) or asexually.
Sexual reproduction is in response to stressful conditions.
Spores are carried by wind or water.
Syngamy - the sexual union of haploid cells from two individuals occurs in two stages.
Plasmogamy - fusion of cytoplasm.
Karyogamy - fusion of nuclei.
After plasmogamy nuclei pair up to form a dikaryon. May exists for months or years. True diploid protection. After karyogamy meiosis immediately follows.
- characterized by the presence of dikaryotic zygosporangia, resistant structures formed during sexual reproduction.
• live in moist soil or decaying organic matter (bread).• Some form mycorrhizae, mutualistic associations with plant roots.
• hyphae are coenocytic - septa are found only in reproductive cells.
Favorable conditions - Sporangia develop at tips of hyphae and produce haploid spores asexually by mitosis.
Unfavorable condition - + and - mating types form gametangia contain several hundred haploid nuclei walled off by a septum.
Plasmogamy occurs forming dikaryotic zygosporangium, inactive and resistant to desiccation and freezing.
When conditions change karyogamy occurs and haploid recombined spores are released.
- includes yeast and multicellular cup fungus-hyphae are septate
- tips of specialized hyphae form conidia, chains of asexual haploid spores.
- sexually, opposite mating strains fuse. an "ascogonium" receives haploid nuclei from antheridium of "male."
The ascogonium grow hyphae with dikaryotic cells.
In terminal cells syngamy occurs
Meiosis forms 4 haploid nuclei, followed by mitosis to form 8 haploid nuclei. the nuclei form walls and become ascospores within an ascus. Multiple asci may form an ascocarp - a fruiting structure with many asci packed together.
Unicellular yeast, bud and reproduce sexually forming the equivalent of conidia and asci.
- mushrooms, shelf fungi, puff balls and stink fungus.
Basidium - transient diploid, spore producing stage.
important decomposers of wood.include mycorrhiza-forming mutualists and plant parasites.
includes mushroom forming mutualist, saprobes and parasites.
Long lived dikaryotic mycelium - produces fruiting bodies called basidiocarps.
Haploid basidospores grow into short lived haploid mycelia. Plasmogamy occurs between different mating strains. Grows as mycorrhizae and in response to cues forms mushrooms (basidiocarps.)
The mushroom cap supports and protects a large surface area of gills. Karyogamy in the terminal cells of the gills produce diploid basidia.
Each basidium undergoes meiosis producing four haploid basidiospores.
Asexual reproduction also results in the formation of conidia.
A. Mold - a rapidly growing , asexually reproducing fungus.
They may be zygomycetes, ascomycetes or basidiomycetes or fungi with no known sexual stage.
Molds with no known sexual stages are classified as Deuteromycota or imperfect fungi.
They do produce conidia and may be closely related to the Ascomycetes.
Deuteromycetes are sources of antibiotics including Penicllium.
B. Yeast - unicellular or can alternate with mycelium. Some are classified as Deuteromycetes if not sexual stages are known.
Others, form asci or basidia.
Bread and alcoholic fermentation.
Saccharomyces cerevisiae - an ascomycete available as baker's yeast.
Yeast Pathogens - Rhodotorula - shower curtains
Candida inhabitant of moist human tissue.
C. Lichen - usually filamentous green algae and fungal hyphae (usually ascomycetes)
alga - provides sugars and may fix nitrogen
fungus provides minerals gas exchange and protection. Fungal pigments can shade and protect alga. Fungal toxins may prevent being eaten.
lichen are foliose (leafy), fruticose (shrubby) or crustose (crusty)
Reproduction as a combined unit or by independent reproduction.
Some fungi produce ascocarps and rarely basidiocarps.
Soredia - combined fragmented clusters of both organisms.
D. Mycorrhizae - increases absorptive surface of roots and exchange of soil minerals.
90% of trees and majority of vascular plants.
are necessary of optimal plant growth.