Fungus plural Fungi Six Kingdoms of Classification Before

Fungus( plural: Fungi) Six Kingdoms of Classification

◎ Before the introduction of molecular methods for phylogenetic analysis, taxonomists considered fungi to be members of the Plant Kingdom because of similarities in lifestyle: both fungi and plants are mainly immobile, and have similarities in general morphology and growth habitat. Like plants, fungi often grow in soil, and in the case of mushrooms form conspicuous fruiting bodies, which sometimes bear resemblance to plants such as mosses. Some morphological, biochemical, and genetic features are shared with other organisms, while others are unique to the fungi, clearly separating them from the other kingdoms

2 n 1 n Life Cycle of Fungus

◎ Fungi lack chloroplasts and are heterotrophic organisms, requiring preformed organic compounds as energy sources. ◎The cells of most fungi grow as tubular, elongated, and filamentous structures and are called hyphae, which may contain multiple nuclei and extend at their tips. In contrast, similar-looking organisms, such as filamentous green algae, grow by repeated cell division within a chain of cells.

◎ Most important of all, the fungal cell wall is composed of glucans and chitin. Chitin is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose. N-Acetylglucosamine is a monosaccharide derivative of glucose.

Phylogenesis

◎ What role do fungi play in food chains? Bacteria and fungi are decomposers. They break down waste products and dead organisms for food. These broken down materials are returned to the soil to be recycled and used by plants again. An example of this would be a fungus growing on a log. ◎ What is the relationship between fungi and other organisms? Nearly all plants depend on symbiotic fungi, known as mycorrhizae, which help their roots absorb minerals and water from the soil. A lichen is a combination of a green alga and a fungus. The alga receives from the fungus both attachment and protection from desiccation; The fungus benefits from the product of photosynthesis released by the alga.

mycorrhizae lichen

◎ What can we benefit from fungi? Fungi are used by humans for food( mushroom) and to produce food ( bread and citric acid) and drugs( alcohol and penicillin). When the anticancer drug taxol, which is produced by yew trees, was discovered, the yew forests of the U. S. Northwest coast would be decimated to harvest the drug. However, the fungus Taxomyces also produces taxol.

And what diseases can fungi cause? Fungal infections can range from being only the epidermis to being deep within the body… To reveal “The Secrets of Fungi” we probe into it from microcosmic and macrocosmic structures of fungi, mechanism of reproduction, evolution, roles in ecosystem, and finally, their application.

1. Microcosmic view 2. Macrocosmic view 3. Reproduction 4. Evolution 5. Roles in ecosystem 6. Application

Microcosmic view Septate hyphae Septum Coenocytic hyphae Septate hyphae have septa( singular: septum), which divide them into distinct, uninucleate( one-nucleus) cell-like units. Coenocytic hyphae contain no septa and appear as long continuous cells with many nuclei.

Septate hyphae

The portion of a hypha that obtains nutrients is called vegetative hypha. The portion concerned with reproduction is the reproductive or aerial hypha.

Filamentous fungi can reproduce asexually and sexually. Conidium (n) Sporangiospore Two types of asexual spores: Conidium( plural: conidia): A multicellular spore that is not enclosed in a sac. Sporangiospore: Formed within sporangium, or sac.

One characteristic feature of fungal sexual reproduction. Zygospore (2 n) Zygosporangium A zygospore results from the fusion of the nuclei of two cells

Sporangium (n) Zygosporangium (2 n)

Budding pseudohypha Some yeasts produce buds that fail to detach themselves, forming a short chain of cells called pseudohypha.

Macrocosmic view - mushroom Fruiting structure (2 n)

Basidiospores(n) are formed by meiosis.

Reproduction Spore of asexsual and sexual reproduction 1. Conidiospore -arthroconidium -blastoconidium -chlamydoconidium 2. Sporangiospore Asexsual reproduction 1. Yeast budding 2. Frangmentation 3. Sporulation Sexual reproduction Always under three steps

Conidiospore a unicellular or multicellular spore that is not enclosed by sac Conidia are produced in a chain at the end of a conidiophore 1. Conidia formed by the fragmentation of a septate hypha into a single, slightly thickened cells are called arthroconidia 2. Another type of conidia consists of buds coming off the parent cell are called blastoconidia 3. The other type of conidia is a thick –walled spore form by roundling and enlargement within a hyphal segment are called chlamydoconidia.

Sporangiospore It is formed within a sporangium(sac) at the end off an hypha

Asexual reproduction 1. Bud formation in yeasts In its simplest form asexual reproduction is by budding or binary fission. The onset of the cellular events is accompanied by the nuclear events of mitosis. The initial events of budding can be seen as the development of a ring of chitin around the point where the bud is about to appear. When chains of yeast cell do not fully seperated this can create a pseudomycelium

2. Fragmentation Many fungi can reproduce by fragmentation. Any mycelium that is fragmented or disrupted, provided that the fragment contains the equivalent of the peripheral growth zone, can grow into a new colony 3. sporulation Asexual reproduction is extremely important to fungi. It is responsible for the production of large numbers of spores throughout the year. These asexual spores are formed on a phase of the fungal life cycle termed as the mitosporic, or anamorphic phase. There can be more than one mitosporic state for each species of fungus, and in some cases the mitosporic state of very different species can look very similar. mitosporic states. The onset of asexual reproduction is controlled by many different things. Some are environmental, like nutrient levels, CO 2 levels, light levels. Others can fungi have internal time clocks and sporulate anyway in a preset part of the fungal life cycle designed to spread and maximize colonization during one season.

Sexual reproduction Sexual spore result from the fusion of nuclei from two opposite matting strains of the same species of fungi. Sexual reproduction always undergos the following three steps 1. Plasmogamy: a haploid nucleus of a donor cell (+) penetrates the cytoplasm Of a recipient cell (-) 2. karyogamy: the (+) and the (-) fuse to form a diploid zygote nucleus. 3. meiosis: the diploid nucleus gives rise to haploid nuclei (sexual), may be genetic recombination. Fungi produce sexual spore less frequently then asexual one.

Some classes of fungi Zygomycota(conjugation fungi) They are saprophytic molds that have coenocytic hyphae. The black bread mold is the one. (the dark sporangiospore inside the sporangium gives it the descriptive name) The asexual spores of them are sporangriospores. The sexual spores are zygospores. (a large spore enclosed in a thick wall)

Microsporidia Are unusual eukaryote because it lacks of mitochondria. Their sexual reproduction has not been observed but probably occurs within the host. Ascomycota A sac fungi, their asexual spores are usually conidia produced in a long chain from the conidiophore. Conidia means dust, meaning that the spore can freely detach from the chain Ascosporeresult from the fusion of two cells that can be either morphologically similar or disimilar. These spores are produced in a saclike structure, called an ascus (that’s what their name come from) Basidiomycota Also called club fungi possess septate hyphae. Basidiospores are formed externally on a base pedestal Called a basidium. Usually four basidiospores per basidium.

By the way , the fungi produce sexual and asexual spores are teleomorphs, the only have asexual are anamorphs.

Evolution

Fossil record l l l In contrast to plants and animals, the early fossil record of the fungi is meager. Fruiting bodies are soft, fleshy, and easily degradable tissues. Often recovered from a permineralized plant or animal host.

l l The earliest fossils date to the Proterozoic eon, 1430 million years ago. In Paleozoic Era (542– 251 Ma), the fungi appear to be aquatic and have flagellumbearing spores.

Landing l l Ecological strategies for obtaining nutrients for a terrestrial lifestyle includes parasitism, saprobism, and the development of mutualistic relationships such as mycorrhiza and lichenization The fungi probably colonized the land during the Cambrian (542– 488. 3 Ma), long before land plants.

l Fungal fossils do not become common and uncontroversial until the early Devonian (416– 359. 2 Ma). Abundant in the Rhynie chert At about the same time, approximately 400 Ma, the Ascomycota and Basidiomycota diverged, and all modern classes of fungi were present by the Late Carboniferous (318. 1– 299 Ma). l l

Role in ecosystem

An important role l l l Fungi occur in every environment on Earth and play very important roles in most ecosystems. Along with bacteria, fungi are the major decomposers in most terrestrial (and some aquatic) ecosystems An essential role in nutrient cycling, especially as saprotrophs and symbionts, degrading organic matter to inorganic molecules

With plants l Mycorrhizal symbiosis between plants and fungi is of significant importance for plant growth and persistence in many ecosystems

With algae and cyanobacteria l l Lichens are formed by a symbiotic relationship between algae or cyanobacteria and fungi Lichens occur in every ecosystem on all continents, play a key role in soil formation and the initiation of biological succession and are the dominating life forms in extreme environments

With insects l l Many insects also engage in mutualistic relationships with fungi Females of several wood wasp species inject their eggs together with spores of the woodrotting fungus Amylostereum areolatum into the sapwood of pine trees