Myxogastrida (plasmodial slime molds) (formerly Myxomycota latter is supplement) (a)Feeding stage consists of a motile, multinucleated, amoeboid mass called a plasmodium (b)"If the habitat of a slime mold begins to dry up or there is no food left, the plasmodium ceases growth and differentiates into a stage of the life cycle that functions in sexual reproduction."sexual reproduction
Plasmodial slime molds, like Physarum shown here, are basically enormous single cells with thousands of nuclei. They are formed when individual flagellated cells swarm together and fuse. The result is one large bag of cytoplasm with many diploid nuclei.
Dictyostelida (cellular slime molds) (formerly Acrasiomycota latter is supplement) (a)Unlike the plasmodial slime molds, the cellular slime molds exist as free-living individual cells that come together to form a multicelled slug (rather than forming a multinucleated plasmodium via multiple rounds of mitosis not followed by cytokinesis as do the plasmodial slime molds)plasmodial slime molds (b) Individual cells resemble amoebasamoebas (c)"The feeding stage of the life cycle consists of solitary cells that function individually. When there is no more food, the cells form an aggregate that functions as a unit. Although the mass of cells resembles a plasmodial slime mold, the important distinction is that the cells of a cellular slime mold maintain their identity and remain separated by their membranes."
Oomycota (water molds) (a) The Oomycota or water molds superficially resemble fungi, but differ from true fungi in a number of ways includingfungi (i) Water molds have cellulose (not chitin) cell walls (ii) Water molds are flagellated at certain points in their life cycle (iii) Water molds are diploid throughout most of their life cycle
"Oomycota" means "egg fungi," and refers to the large round oogonia, or structures containing the female gametes, as shown in this picture of the common "water mold" Saprolegnia. Oomycetes are oogamous, producing large non-motile gametes called eggs, and smaller gametes called sperm
Fungii Ancient Greeks and Egyptians used fungii to make wine Myan Indian tribes of Mexico, hallucinogenic mushrooms in religious ceremonies World War I, puff balls were used to cover wounds Pathogens to humans, plants and other organisms Environmental recyclers
Fungal Structure Eukaryotic, multicelllular Filaments (hyphae), connected end to enc Diffuse connection of cells, body of a fungii is termed mycellium Reproductive hyphae for the sporocap (cap of the mushroom)
Fungal Cells In addition to being filamentous, fungus may be coenocytic, no distinction between individual cells. Long filaments with a cytoplasm lining and a large vacuole in the center. (zygomycetes) Others are septate,filaments are separated by cross walls called septa (ascomycetes and basidiomycetes)
Hyphae grow at their tips and branch to form a mass of interwoven strands that is called mycelium.
Ploidy Fungi typically possess haploid nuclei, except just prior to meiosishaploidnucleimeiosis Only following nuclear fusion (karyogamy) are fungi diploid, and mitosis in fungi does not occur in the diploid statekaryogamydiploid mitosis However, many fungi routinely achieve a diploid-like state following cytoplasmic fusion (plasmogamy) that is called a dikaryon state or stage; note that dikaryon is not synonymous with diploid since nuclei remain haploid even if found in same cytoplasmcytoplasmic fusionplasmogamy dikaryon
Plasmogamy Though fungi nuclei are typically haploid, that doesn't stop haploid nuclei from different fungal parents (e.g., mom and dad equivalents) from being present in the same cytoplasm haploidcytoplasm The process by which the cytoplasms of two parental fungi fuse is called plasmogamy Note that plasmogamy may be followed by nuclei fusing, though this does not necessarily occur immediately, and for some fungi the time until nuclear fusion occurs can be greatly extended (days, months, years)
Dikaryon state or stage The post-plasmogamy condition in which two different haploid nuclei occupy the same cytoplasm is a dikaryon state or stageplasmogamyhaploidcytoplasm Being a dikaryon, since cytoplasms are shared, provides the masking of deleterious alleles of diploidy without the possession of diploid nucleidiploidy
Karyogamy The fusion of haploid nuclei found in dikaryonic fungal cells is called karyogamyhaploid dikaryonic Karyogamy is necessary for the occurrence of meiosis (since haploid nuclei cannot undergo meiosis)meiosis Note that meiotic products are both haploid and therefore are no longer dikaryonic
Sexual Reproduction Sexual reproduction (note: order of terms is relevant): mitosis HyphaeHyphae (ploidy = n) mitosis MyceliumMycelium (ploidy = n) PlasmogamyPlasmogamy (a process) (= fusion of cytoplasm) Dikaryotic stageDikaryotic stage (ploidy = n + n) (occurs within zygosporangia for Zygomycete, ascogonia for Ascomycete, or hyphae for Basidiomycete)ZygomyceteascogoniaAscomycetehyphaeBasidiomycete mitosis KaryogamyKaryogamy (a process) (= fusion of haploid nuclei) Diploidy (ploidy = 2n) (occurs within zygosporangia for Zygomycete, ascocarps for Ascomycete, or basidiocarps for Basidiomycete) ZygomyceteascocarpsAscomycetebasidiocarps Basidiomycete MeiosisMeiosis (a process) Spore-producing structures (ploidy = n) (= sporangium for Zygomycete, asci for Ascomycete, or basidia for Basidiomycete) ZygomyceteasciAscomycetebasidia Basidiomycete Spores (ploidy = n) (= spores for Zygomycete, ascospores for Ascomycete, or basidiospores for Basciomycete)ZygomyceteascosporesAscomyceteBasciomycete Germination (a process) mitosis HyphaeHyphae (ploidy = n) mitosis MyceliumMycelium (ploidy = n)
Asexual reproduction (note: order of terms is relevant): mitosis HyphaeHyphae (ploidy = n) mitosis MyceliumMycelium (ploidy = n) mitosis Spore-producing structures (ploidy = n) mitosis Spores (ploidy = n) (= conidia for sac fungi)conidia Germination (a process) mitosis HyphaeHyphae (ploidy = n) mitosis MyceliumMycelium (ploidy = n)
Placement into a division is based on the way in which the fungus reproduces sexually. The shape and internal structure of the sporangia, which produce the spores, are the most useful character for identifying these various major groups. There are also two conventional groups which are not recognized as formal taxonomic groups (ie. they are polyphyletic
Club Fungi (Basidiomycota) latticed stinkhorn Species in this phylum produce spores on a club-like structure called the basidium
Produce spores on exposed surfaces -- releasing the spores gradually through structures such as pores or gills.
Division Basidiomycota (club fungi, mushrooms) Members of Division Basidiomycota are also called the club fungi and include the mushrooms Mushrooms are fruiting bodies of underground myceliamycelia Club fungi spend most of their life cycle in the dikaryotic statedikaryotic
Basiodospores (mushroom gill)
Sac Fungi (Ascomycota) Sac fungi produce spores inside cases (asci) which may open at one end.
White Morel (Morchella deliciosa, left), however, is often found in urban locations growing among leaves or other discarded stuff.
Another prominent group of Ascomycota is the Cup Fungi The mushrooms of these fungi look like little cups or sacs and often do not have a stalk at all. An exception to this is the brightly colored Stalked Orange Peel Fungus (Aleuria rhenana).
In hyphal Ascomycota, the youngest, terminal hyphal segments develop into 8- spored asci.
Ascomycota are either single-celled (yeasts) or filamentous (hyphal) or both (dimorphic). Yeasts grow by budding or fission and hyphae grow apically and branch laterally. Most yeasts and filamentous Ascomycota are haploid, but some species, Saccharomyces cerevisiae for example, can also be diploid. Mitospores may simply reproduce the parent, or may also act as gametes to fertilize a compatible partner.
Conjugation Fungi (Zygomycota) The best known of this phylum of around 600 species is black bread mold, such as Rhizopus stolonifer.
Division Zygomycota (zygote fungi) These are the zygote fungi In their sexual cycle these fungi form gametangia that are multinucleated cells walled off from parental cells by septa gametangiasepta Gametangia from two different parental fungi fuse (undergo plasmogamy) to form dikaryonic zygosporangia that are capable of toughening to form a dormant stage plasmogamy dikaryonic
Zygosporangia give rise to sporangia following germination, karyogamy, and meiosis sporangia karyogamymeiosis
Imperfect Fungi (Deuteromycota) Around 25,000 additional fungus species are grouped in this phylum -- these species are the "left-overs" that don't fit well into any of the other groups. Members include Trichophyton (Athlete's foot), Penicillium (Penicillin), and Candida albicans ("Yeast" infections).
Imperfect fungi Imperfect fungi fail to reproduce sexually, consequently fail to produce the sexual structures by which other fungi are classified (at least traditionally), so are not well phylogenetically classified, at least using classical methodsreproduce sexually
Lichens are a polyphyletic grouping of fungi that possess algae (eukaryotic or blue-green) symbiontspolyphyleticfungiblue-green "The fungus usually gives the lichen its overall shape and structure, and tissues formed by hyphae account for most of the lichen's mass… The alga always provides the fungus with food. Cyanobacteria in lichens fix nitrogen and provide organic nitrogen. The fungus provides the alga with a suitable physical environment for growth. Lichens absorb most of the minerals they need either from air or in the form of dust… Fungal pigment shades the algae from intense sunlight. Some fungal compounds are toxic and prevent lichens from being eaten by consumers." hyphae Cyanobacteriafix nitrogenconsumers
Crustose Lichens Crustose lichens are flaky or crust-like. They can be found covering rocks, soil, bark, etc. -- often forming brilliantly colored streaks. The yellow ones pictured here on a granite stone in the Rocky mountains, are probably Common Yolk Lichens (Acarospora spp.); the red, Caloplaca spp.; and green, Lecanora spp.. The little buttons to the left are a magnification of the red streaks above.
Foliose Lichens Foliose (leaf-like) lichens can be papery thin or, in more advanced forms, netted branch-like. Branched foliose lichens have a distinct top and bottom surface, thus differentiating them from most fruticose lichens. This can be seen clearly in the Pseudocyphellaria anthraspis photo, above left; the Hypogymnia imshaugii on the right has a puffed body with a black undersurface.
Fruticose Lichens Fruticose lichens are the most highly developed lichens. Their branches are much closer in form to "true" branches although, unlike most plants, the lichen branch has no specialized vascular system for transporting fluids. The British Soldier Lichen (Cladonia macilenta), left, is one of the showiest fruiting lichens: even though the mushrooms are quite tiny, their bright color and distinctive form makes them stand out in their forest habitat.