University:
Brigham Young University
Course:
MMBIO 221 | General Microbiology
Academic year:

2023
Views:

296

Pages:

14
Author:

do3ran7ut

INTRODUCTION TO FUNGI The Characteristics of Fungi • Body form * unicellular * filamentous (tube-like strands called hypha (singular) or hyphae (plural) * mycelium = aggregate of hyphae * sclerotium = hardened mass of mycelium that generally serves as an overwintering stage. * multicellular, such as mycelial cords, rhizomorphs, and fruit bodies (mushrooms) fruiting bodies both are composed of hyphae mycelium • Tubular • Hard wall of chitin • Crosswalls may • • form compartments (± cells) Multinucleate Grow at tips 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). Properties of Fungi • Heterotrophy - 'other food' * Saprophytes or saprobes - feed on dead tissues or organic waste (decomposers) * Symbionts - mutually beneficial relationship between a fungus and another organism * Parasites - feeding on living tissue of a host. • Parasites that cause disease are called pathogens. Fungi as Saprobes and Decomposers Fungi as Symbionts (Mutualism) 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 “Ecto”mycorrhizae Russula mushroom mycorrhizas on Western Hemlock root Fungal hyphae around root and between cells Mycorrhiza cross sections • • 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. Fungi as Parasites & Pathogens Fungi are 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 • Formed: * Sexual (meiotic in origin) * Asexual (mitotic in origin) * Directly on hyphae * Inside sporangia * Fruiting bodies Pilobolus sporangia Amanita fruiting body Penicillium hyphae with conidia