Fungi
A member of the Eukarya, fungi live by absorptive nutrition in which they secrete digestive enzymes to break down large molecules in the environment. They are composed of rapidly growing filamental hyphae and are distinguished by their cell walls which contain microscopic fibrils of chitin, a nitrogen containing polysaccharide.
Phylum Chytridiomycota
This group consists of unicellular, aquatic basal fungi that possess flagellated gametes and zoospores in their life cycle.
A. macrogynus is a type of water mold, widely distributed throughout the worlds fresh water environments. They are the only fungal group to demonstrate true alternation of generation between multicellular haploid cells and multicellular diploid cells. The life cycle begins when a haploid zoospore locates a suitable substrate, such as a dead plant or animal material, in water where it germinates and divides to form a small mycelium. This mycelium produces gametangia which encase male and female flagellated, haploid gametes. The motile female gamete produces sirenin, a pheromone, to attract male gametes. Sirenin acts as a chemical signal for the male gametes to swim toward the female gametes where they fuse to form a diploid zygote. Through mitosis and cytokinesis, the zygote gives rise to a small, diploid organism that produces more diploid zoospores that are dispersed to form more diploid organisms. Eventually, the cell walls of the diploid organism will thicken, becoming sporangia capable of surviving under numerous unfavorable conditions. It is believed that the purpose of the multicellular haploid stage is to serve as a filter for any harmful mutations that may occur. Organisms with mutations would die, preventing the mutant allele from being passed on to the next generation.
Phylum Zygomycota
This group is considered the most primitive terrestrial fungi. Spores and gametes lack flagellated cells and the zygote is the only diploid cell in their life cycle. While their hyphae occasionally have stalked spore containing sporangiophores, they lack any fleshy fruiting structure.
Class Zygomycetes
The Zygomycetes consists of terrestrial saprotrophs, symbionts, and parasites with well developed mycelium which can be immersed in substrate or host tissue.
The Zygomycetes consists of terrestrial saprotrophs, symbionts, and parasites with well developed mycelium which can be immersed in substrate or host tissue.
Pilobolus roridus
P. roridus is an obligate coprophile and can be found in large numbers on the fresh dung of herbivorous ruminants and farm animals. Their life cycle begins when their spores are eliminated from by the animal. Unable to produce their own food, they feed on undigested minerals as well as plant and bacterial matter contained in the manure in which they reside through their extensive hyphae and mycelium. As the fungus feeds and grows, reproductive fruiting bodies form. Within the fruiting bodies are small, black, apical sporangia containing the asexual spores. In order to continue the life cycle, it is essential that spores are ingested and travel through the GI tract of an animal. To do so, P. roridus is capable of launching their sporangia up to 6 feet away. The further they are away from their original location in the dung piles, significantly increases their chances of becoming consumed when a herbivore is grazing. This species also has evolved an unique association with a larval roundworm species which causes lung worm in herbivorous animals. As the sporangia mature, the larva climb to their ends where, along with the spores, they are catapulted away from the dung piles.
Phylum Ascomycota
Phylum Ascomycota is the largest fungal group, containing marine, fresh water, and terrestrial species. They are recognized as cup fungi in which their fruiting bodies contain ascospores which are involved in sexual reproduction.
Class Saccharomycetes
This group consists of hemiascomycetes, or budding yeasts, which lack the characteristic ascocarp, are unicellular and microscopic.
Saccharomyces cerevisiae
This species of yeast appears round or ovoid in shape and can be found on the skins of grapes and other dark colored fruits. Asexual reproduction for this yeast occurs through fission in which the haploid cells split after mitosis, or by budding. Sexual reproduction occurs when two haploid cells of opposite mating types, a and α, fuse. The fusion between the two cells forms sacs called asci that contain multiple haploid ascospores. S. cerevisiae grows aerobically on glucose, maltose, and trehalose, and can use ammonia, urea, and most amino acids as sources of nitrogen. Commercially, this species is most commonly known for its role in brewing beer. During this process, the yeast ferments glucose to ethanol and carbon dioxide. In bread making, carbon dioxide produced becomes trapped within the dough as tiny air bubbles, causing it to rise, and gives bread its light texture.
Phylum Glomeromycota
This group of fungi are strictly terrestrial species where they are obligate biotrophs, depending on their symbioses with plants for energy. They are only capable of performing asexual reproduction.
Geosiphon pyriformis
G. pyriformis is known for its obligatory symbiotic relationship it forms with Nostoc species of Cyanobacteria. This interaction occurs in the upper layers and surface of moist soils where fungal hyphae engulf a specific stage of the Nostoc, forming a siphonal bladder structure around the bacteria. The bladder is unicellular and multi-nucleated; its morphology is characterized as a swollen hyphal cell. It is the site of carbon dioxide fixation, nitrogen fixation, and photosynthesis where the Nostoc acts as the primary photosynthetic agent for G. pyriformis. Due to the complex design of the bladder walls, they act as an osmotic barrier, limiting the exchange of nutrients from the surrounding environment. Thus, it is essential that the fungus synthesize its carbon sugars internally with its bacterial symbiont. While this species of Glomeromycota does not form arbuscular mycorrhizae with plants, the function of the bladder and Cyanobacteria is homologous to that of fungal-plant associations. Asexual reproduction in this species occurs through the production of fungal spores which are positioned at the end of hyphae or within hyphae cells.
Phylum Basidiomycota
The Basidiomycota are known as the club fungi in which their fruiting bodies sexual basidiocarps. They all have a long dikaryon stage.
Class Agaricomycetes
The morphology of the Agaricomycetes is extremely diverse. They play a major ecological role as wood-decayers and ectomycorrhizal symbionts of forest trees. The majority of edible mushrooms are in this group as well as those that possess hallucinogenic compounds.
Trametes versicolor
This species is a saprobic mushroom found in moist, shady areas arranged in clusters of overlapping shelves on stumps or logs of decaying hardwoods. They are also commonly known as turkey tail because of their characteristic morphology. The fan-shaped caps consist of thin, leathery shelves with multicolored bands of black, brown, tan, white, yellow, and red. The underside of the caps contains a layer of small, visible white pores. T. versicolor is most notably known for its healing properties. The sugar, polysaccharide-k (PSK), isolated from its fruiting bodies, is used to boost the immune system for patients going through cancer treatment in some European countries as well as in China and Japan. Further research has proved that this sugar can reduce mutagen, radiation, and spontaneously induced cancers by stimulating host mediated response. Additionally, it is known as a reverse transcriptase inhibitor of recombinant HIV-1.