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 The life cycle of basidiomycetes, better known as mushrooms, is shown. Basidiomycetes have a sexual life cycle that begins with the germination of 1n basidiospores into mycelia with plus and minus mating types. In a process called plasmogamy, the plus and minus mycelia form a dikaryotic mycelium. Under the right conditions, the dikaryotic mycelium grows into a basdiocarp, or mushroom. Gills on the underside of the mushroom cap contain cells called basidia. The basidia undergo karyogamy to form a 2n zygote. The zygote undergoes meiosis to form cells with four haploid (1n) nuclei. Cell division results in four basidiospores. Dispersal and germination of basidiospores ends the cycle.
The lifecycle of a basidiomycete alternates generation with a prolonged stage in which two nuclei (dikaryon) are present in the hyphae.

Deuteromycota:

Those fungi that do not display a sexual phase and only reproduce by mitospores are classified in the form phylum Deuteromycota . Deuteromycota is a polyphyletic group where many species are more closely related to organisms in other phyla than to each other; hence it cannot be called a true phylum and must, instead, be given the name form phylum. Since they do not possess the sexual structures that are used to classify other fungi, they are less well described in comparison to other divisions. Most members live on land, with a few aquatic exceptions. They form visible mycelia with a fuzzy appearance and are commonly known as mold . Molecular analysis shows that the closest group to the deuteromycetes is the ascomycetes. In fact, some species, such as Aspergillus, which were once classified as imperfect fungi, are now classified as ascomycetes.

Reproduction of Deuteromycota is strictly asexual and occurs mostly by production of asexual conidiospores ( [link] ). Some hyphae may recombine and form heterokaryotic hyphae. Genetic recombination is known to take place between the different nuclei.

 Micrograph shows Aspergillus mycelia, which look like long threads, and a spherical conidiophore about 40 microns across.
Aspergillus niger is an imperfect fungus commonly found as a food contaminant. The spherical structure in this light micrograph is a conidiophore. (credit: modification of work by Dr. Lucille Georg, CDC; scale-bar data from Matt Russell)

The Deuteromycetes have a large impact on everyday human life. The food industry relies on them for ripening some cheeses. The blue veins in Roquefort cheese and the white crust on Camembert are the result of fungal growth. The antibiotic penicillin was originally discovered on an overgrown Petri plate, on which a colony of Penicillium fungi killed the bacterial growth surrounding it. Many imperfect fungi cause serious diseases, either directly as parasites (which infect both plants and humans), or as producers of potent toxic compounds, as seen in the aflatoxins released by fungi of the genus Aspergillus .

Glomeromycota: the mitosporic fungi

The Glomeromycota is a newly established phylum which comprises about 230 species that all live in close association with the roots of trees. Fossil records indicate that trees and their root symbionts share a long evolutionary history. It appears that all members of this family form arbuscular mycorrhizae : the hyphae interact with the root cells forming a mutually beneficial association where the plants supply the carbon source and energy in the form of carbohydrates to the fungus, and the fungus supplies essential minerals from the soil to the plant.

The glomeromycetes do not reproduce sexually and do not survive without the presence of plant roots. Although they have coenocytic hyphae like the zygomycetes, they do not form zygospores. DNA analysis shows that all glomeromycetes probably descended from a common ancestor, making them a monophyletic lineage.

Pathogenic fungi

Many fungi have negative impacts on other species, including humans and the organisms they depend on for food. Fungi may be parasites, pathogens, and, in a very few cases, predators.

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Source:  OpenStax, Principles of biology. OpenStax CNX. Aug 09, 2016 Download for free at http://legacy.cnx.org/content/col11569/1.25
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