Fungi Characteristics PDF

fungi have a combination of characteristics 1. Achlorophyllous: Fungi cannot make their own food like plants. They are heterotrophs and depend upon other organism for their carbon source. Heterotrophs can further be divided into the following categories: a. Parasites: Organisms that derives thei...

fungi have a combination of characteristics 1. Achlorophyllous: Fungi cannot make their own food like plants. They are heterotrophs and depend upon other organism for their carbon source. Heterotrophs can further be divided into the following categories: a. Parasites: Organisms that derives their nutrition from the protoplasm of another organism (=host). feeding on living tissue of a host. Parasites that cause disease are called pathogens. b. Saprobes: Organisms that obtains their carbon source (=food) from the by- products of organisms or dead organisms. However, if the opportunity arises, some saprobes may become parasitic. Such organisms are said to be facultative parasites. feed on dead tissues or organic waste (decomposers) C. Symbiosis: In the strict sense, this term refers to the habitual "living together" of different species. "Intimate association of two dissimilar organisms in a mutually beneficial relationship, e.g. lichens and mycorrhizae." This type of symbiosis is specifically referred to as a mutualistic symbiosis. mutually beneficial relationship between a fungus and another organism. 2. Eukaryotic: Fungi have membrane bound organelles, i.e. nucleus, mitochondrion, E.R., etc. Once upon a time filamentous bacteria called Actinomycetes were classified with fungi, but this is no longer the case. 3. The vegetative body of the fungus (=thallus) are one of the following forms: Yeast: Unicellular fungi that reproduce, asexually, by budding or fission (terms to be defined later).  Mycelium: The collective, filamentous strands that make up the fungal thallus (molds). Strands of mycelium is referred to as hyphae (sing.=hypha). Mycelium may be of two types: Septate: Mycelium that is divided into discreet cells by cell walls that are laid down at regular intervals along the length of the mycelium. These cell walls are called septa (sing.= septum). Coenocytic: Mycelium that is not divided up by septa and forms a continuous tubular network. Septa, however, are present occasionally, especially where reproductive structures occur and where the cell wall of the mycelium has been compromised. Some species may have thalli that are mycelium and yeast. Such fungi are said to be dimorphic (=two forms). mycelium: septate mycelium: Aseptate fruiting bodies both are composed of hyphae mycelium Heterotrophic by Absorption Fungi get carbon from organic sources Hyphal tips release enzymes Enzymatic breakdown of substrate Products diffuse back into hyphae Nucleus hangs back and “directs” Product diffuses back into hypha and is used  Hyphae Tubular Hard wall of chitin Cross-walls may form compartments (± cells) Multinucleate, having more than one nucleus Grow at tips Nuclei of fungi are hard to see without stains  Hyphal growth  Hyphae grow from their tips  Mycelium = extensive, feeding web of hyphae  Mycelia are the ecologically active bodies of fungi This wall is rigid Only the tip wall is plastic and stretches  Mycorrhizae “Fungus roots” Mutualism between: Fungus (nutrient & water uptake for plant) Plant (carbohydrate for fungus) Several kinds Zygomycota – hyphae invade root cells Ascomycota & Basidiomycota – hyphae invade root but don’t penetrate cells Extremely important ecological role of fungi!  Lichens “Mutualism” between Fungus – structure Alga or cyanobacterium – provides food  Three main types of lichens:  Crustose lichens form flat crusty plates.  Foliose lichens are leafy in appearance, although lobed or branched structures are not true leaves.  Fruticose lichens are even more finely branched and may hang down like beards from branches or grow up from the ground like tiny shrubs.  Fungal Spore  Spores - asexual (product of mitosis) or sexual (product of meiosis) in origin.  Purpose of Spores Allows the fungus to move to new food source. Resistant stage - allows fungus to survive periods of adversity. Means of introducing new genetic combinations into a population  Reproduce by spores Spores are reproductive cells Sexual (meiotic in origin) Asexual (mitotic in origin) Formed: Directly on hyphae Inside sporangia Penicillium hyphae Fruiting bodies with conidia Pilobolus sporangia Amanita fruiting body  Hyphal growth from spore germinating spore mycelium Mycelia have a huge surface area  The Characteristics of Fungi  Fungus is often hidden from view. It grows through its food source (substratum), excretes extracellular digestive enzymes, and absorbs dissolved food.  Indeterminate clonal growth.  Vegetative phase of fungus is generally sedentary.  Cell wall present, composed of cellulose and/or chitin.  Food storage - generally in the form of lipids and glycogen.  Eukaryotes - true nucleus and other organelles present.  All fungi require water and oxygen (no obligate anaerobes).  Fungi grow in almost every habitat imaginable, as long as there is some type of organic matter present and the environment is not too extreme.  Diverse group, number of described species is somewhere between 69,000 to 100,000 (estimated 1.5 million species total).