微生物学史微生物学史 (15).ppt

Overview of FungiAfter learning this section,you should be able to:Discuss the importance of fungi in the environment as well as their practical importance The term fungus(pl.,fungi)describes eukaryotic organisms that are spore-bearing,have absorptive nutrition,lack chlorophyll,and reproduce both sexually and asexually.Scientists who study fungi are mycologists,and the scientific discipline devoted to fungi is called mycology.The study of fungal toxins is called mycotoxicology,and the diseases caused by fungi in animals are known as mycoses(s.,mycosis).Here we present six major fungal groups:Chytridiomycota Zygomycota GlomeromycotaAscomycota BasidiomycotaMicrosporidia(a)Some chytrids,including members of the genus Hypochytrium,are plant parasites,whereas others are free living.(b)Pilabolus sp.,a zygomycete,grows on animal dung and on culture medium.Stalks about 10 mm long contain dark,spore-bearing sacs.(c)Spores of Glomus intraradices,a glomeromycete associated with roots.(d)The cup fungus Cookeina tricholoma is an ascomycete from the rain forest of Costa Rica.In cup fungi,the spore-producing structures line the cup;in basidiomycetes that form mushrooms such as Amanita sp.they line the gills beneath the cap of the mushroom.(e)Basidiomycota-Pleurotus ostreatus,the oyster mushroom,is a basidiomycete.All visible structures of fungi arise from an extensive network of hyphae that penetrate and are interwoven with the substrate as they grow.(f)Microsporidia-The unusual fungi that belong to Microsporidia form spores that germinate in host cells.Shown here is the mosquito pathogen Edhazardia aedis.Fungi are primarily terrestrial organisms.They have a global distribution from polar to tropical regions.Fungi are saprophytes,securing nutrients from dead organic material by releasing degradative enzymes into the environment.Fungi are important decomposers.Many fungi are pathogenic,with over 5,000 species known to attack economically valuable crops and many other plants.About 20 new human fungal pathogens are documented each year.Conversely,fungi also form beneficial relationships with other organisms.For example,the vast majority of vascular plant roots form important associations with fungi called mycorrhizae.Fungi,especially yeasts(single-celled fungi),are essential to many industrial processes involving fermentation.Examples include the making of bread,wine,beer,cheeses,and soy sauce.They are also important in the commercial production of many organic acids(citric,gallic)and certain drugs(ergometrine,),and in the manufacture of many antibiotics(penicillin,griseofulvin)and the immunosuppressive drug cyclosporine.In addition,fungi are important research tools in the study of fundamental biological processes.Cytologists,geneticists,biochemists,biophysicists,and microbiologists regularly use fungi in their research.The yeast Saccharomyces cerevisiae is the best understood eukaryotic cell.It has been a valuable model organism in the study of cell biology,genetics,and cancer.Fungal Structure The body or vegetative structure of a fungus is called a thallus(pl.,thalli).It varies in complexity and size.Single-cell microscopic fungi are referred to as yeasts,while multicellular masses are called molds.Fungi also include macroscopic puffballs and mushrooms.Like most bacteria,fungi possess cell walls;however,fungal cell walls are usually made of chitin.Chitin is a strong but flexible nitrogen containing polysaccharide consisting of N-acetylglucosamine residues.Instead of chitin,some fungal cell walls are composed of other polysaccharides such as mannans,galactosans,or cellulose.1.Fungi usually grow better in an acidic pH(5.0),which is too acidic for the growth of most common bacteria.2.Most molds are aerobic,so they grow on surfaces rather than throughout a substrate.Yeasts are facultative anaerobes.3.Most fungi are more resistant to osmotic pressures than bacteria are;most fungi are therefore able to grow in high sugar or salt concentrations.Fungi differ from bacteria in certain environmental requirements and in the following nutritional characteristics:4.Fungi are capable of growing on substances with a very low moisture content,generally too low to support the growth of bacteria.5.Fungi require somewhat less nitrogen for growth than bacteria.6.Fungi are capable of using complex carbohydrates,such as lignin(wood),that most bacteria cannot metabolize.Classification of fungin The classification of fungi,unlike that of bacteria,is based primarily on the characteristics of the sexual spores and fruiting bodies present during the sexual stages of their life cycles.n However,the perfect life cycle of many fungi are yet unknown.They are placed in a special class of Deuteromycetes.FungihyphaerepresentivesSexual sporeZygomycetesNon-septateMucor;Rhizopus ZygosporeAscomycetesSeptateNeurospora;SaccharomycesAscosporeBasidiomyctesSeptateAgaricus;amanitaBasidiosporeDeuteromycetesSeptateAspergillus;PenicilliumNot foundClassification and major properties of fungiWordlist1.fungus(pl.,fungi)真菌2.sexually and asexually 有性和无性3.Mycologists真菌学家4.Mycology 真菌学5.Mycotoxicology真菌毒素6.Mycoses真菌病 mycosis（单数）7.Chytridiomycota壶菌门,Zygomycota接合菌门,Glomeromycota球囊菌门,Ascomycota子囊菌门,Basidiomycota担子菌门,Microsporidia小孢子菌门8.terrestrial organisms陆生生物9.Saprophytes腐生菌10.Decomposer分解者11.Mycorrhizae菌根12.Yeasts 酵母 13.Griseofulvin灰黄霉素14.Ergometrine15.Cytologists 细胞学家,geneticists遗传学家,biochemists,生化学家 biophysicists生物物理学家16.Saccharomyces cerevisiae酿酒酵母17.thallus(pl.,thalli)菌体18.Mold霉菌19.Macroscopic宏观的，肉眼可见的20.Chitin几丁质21.Mannans甘露糖,galactosans半乳聚糖,or cellulose纤维素22.N-acetylglucosamine n-乙酰氨基葡糖Wordlist23.acidic 酸性的24.aerobic 好氧的25.substrate 底物26.facultative 兼性的27.anaerobes 厌氧菌28.osmotic pressure 渗透压29.lignin 木质素30.Deuteromycetes 半知菌纲