華中科技大雙語微生物4

1、Chapter 4 Eukaryotic Microorganisms1Chapter outline4.1 Eukaryotic cell structure4.2 Fungal growth and reproduction4.3 Major group and properties of fungi4.4 Yeasts4.5 Slime molds4.6 Protozoa4.7 Algae2 Concepts Eukaryotes, genetic material is distributed between cells by the highly organized , comple

2、x processes called mitosis and meiosis. Eukaryotic cells differ most obviously from prokaryotic cells in having a variety of membranous organells in the cytoplasmic matrix and the majority of their genetic material within membrane-delimited nuclei. Eukaryotes are heterotrophic microorganisms.34.1 Eu

3、karyotic cell structureCytoplasmicmembraneRibosomesCytoplasmMitochondrionNuclear membraneNucleusNucleolusEndoplasmicreticulumChloroplast4The eukaryotic cell is more complex. All eukaryotes contain a membrane-enclosed nucleus. The eukaryotic cell can be enclosed by a cell wall or cell walls may be ab

4、sent . Organelles are universal among eukaryotic cells while chloroplasts are found only in photosynthetic cells.5 Molds Mushrooms Fungi Yeasts Algae Protozoa Eukaryotic Microorganisms6Major differences among fungi, algae and protozoans7Protozoa are animallike protists exhibiting heterotrophic nutri

5、tion and they can be def- ined as usually motile eukaryotic unicellular microorganisms.Fungi are heterotrophic eukaryotic microorga- nisms. They are nonphotosynthetic and typically form reproductive spores.Algae are phototrophic eukaryotes that contain photosynthetic pigments within a structure call

6、ed the chloroplast8Fungi contain cell walls and produce spores, most described species form a relatively tight phylogenetic cluster.the moldsthe yeasts the mushrooms4.2 Fungal growth and reproduction Three major groups of fungi are recognized:9The molds are filamentous fungi. They are widespread in

7、nature. Each filament grows mainly at the tip, by extension of the terminal cell . Molds A single filament is called a hypha (plural, hyphae). Hyphae usually grow together across a surface and form compact tufts, collectively called a mycelium, which can be seen easily without a microscope10In most

8、cases, the vegetative cell of a fungal hypha contains more than one nucleus, often hundreds of nuclei are present. Even if a hypha has cross-walls, cytoplasmic movement is often not prevented, as there is usually a pore in the center of the septum through which nuclei and cytoplasmic particles can m

9、ove.11nonseptate(2)septate12 The morphology Reproduction Classification Typical species Filamentous fungi13The morphology of filamentous fungiThe filamentous fungi consists of two parts: the mycelium and the spores.A typical hypha is a nucleated tube containing cytoplasm. Usually there is extensive

10、cytoplasmic movement within a hypha, generally in a direc-tion toward the hyphal tip, and the older portions of the hypha usually become vacuolated and virtually devoid of cytoplasm. Each hypha is about 5-10 um wide.14ReproductionAsexual spores are formed by the aerial mycelium of one organism. When

11、 these spores germinate, they become organisms that are genetically identical to the parent. Sexual spores result from the fusion of nuclei from two opposite mating strains of the same species of fungus. Organisms that grow from sexual spores will have genetic characteristics of both parental strain

12、s.15Asexual spores are produced by an individual fungus through mitosis and subsequent cell division; there is no fusion of the nuclei of cells. Several types of asexual spores are produced by fungi. Asexual Spores16Main types of asexual sporesSporangiosporesConidiosporesArthrosporesChlamydospores17

13、Sporangiospores Sporangiospores are formed within a sporangium 18Rhizopus (class Zygomycetes): These are common bread molds, which cause much food spoilage. They have nonseptate. It forms rootlike hyphae called rhizoid, as well as stolons. Zygospores are produced when plus and minus strains are both

14、 present.rhizoidSporangiospores 19Chlamydospores are thick-walled cells within the hyphae Chlamydospores20Arthrospores21ConidiosporesConidiospores are arranged in chains at the end of a conidiophore 22Conidiospores23Name of fungus Location of spores ExamplesChlamydosporeExternalMucor racemosusArthro

15、sporeExternalGeotrichum candidumConidiospore ExternalAspergillus nigerPenicillium notatumSporangiospore InternalRhizopus oryzaeAsexual spores of filamentous fungi24Some molds also produce sexual spores, formed as a result of sexual reproduction. The latter occur from the fusion either of unicellular

16、 gametes or of specialized hyphae called gametangia. Alternatively, sexual spores can originate from the fusion of two haploid cells to yield a diploid cell, which then undergoes meiosis and mitosis to yield individual spores. Sexual Spores25A haploid nucleus of a donor cell (+) penetrates the cytop

17、lasm of a recipient cell (Plasmogamy).The (+) and (-) nuclei fuse to form a diploid zygote nucleus (Karyogamy).By meiosis, the diploid nucleus gives rise to haploid nuclei (sexual spores), some of which may be genetic recombinants (Meiosis).A fungal sexual spore results from sexual reproduction, con

18、sisting of three phases:26Several types of sexual spores Oospores Zygospores Ascospores Basidiospores27Oospores formed within a special female structure, the oogonium. Fertilization of eggs, or oospheres, by male gametes in an antheridium give rise to oospores.antheridiumoospheresoosporesoogoniumOos

19、pores formation28Zygospores are large, thick-walled spores formed when the tips of two sexually compatible hyphae of certain fungi fuse together. Zygospores29Zygospores30Ascospores are single-celled ,they are produced in a sac called an ascus. There are usually 8 as-cospores in each ascus.Various as

20、cocarps formed by different ascomycete fungi.plectocarppyrenocarpdiscocarpAscospores31Basidiospores are single-celled spores, they are borne on a club-shaped structure called basidium.Basidiospores3233FungihyphaerepresentivesSexual sporeZygomycetesNon -septateMucor; RhizopusZygosporeAscomycetesSepta

21、teNeurospora;SaccharomycesAscosporeBasidiomyctesSeptateAgaricus;amanitaBasidiosporeDeuteromycetesSeptateAspergillus;PenicilliumNot found4.3 Major group and properties of fungi34Classification of fungi The classification of fungi is based primarily on the characteristics of the sexual spores and frui

22、ting bodies present during the sexual stages of their life cycles. The perfect life cycle of many fungi are yet unknown. They are placed in a special class of Deuteromycetes35Typical species of filamentous fungiMucor (class Zygomycetes): occur in soil and on fruits, vegetables and starchy foods. Som

23、e are used in the manufacture of cheeses. Their mycelium are nonseptate and are white or gray. Zygospores are produced when plus and minus strains are both present. No stolons or rhizoids.36Rhizopus (class Zygomycetes): these are common bread molds, which cause much food spoilage. They have nonsepta

24、te. It forms rootlike hyphae called rhizoid, as well as stolons. Zygospores are produced when plus and minus strains are both present.37Neurospora (Class Ascomycetes) : this genus is widely used in the study of genetics and metabolic pathways. Some species are responsible for food spoilage, and some

25、 species are used in industrial fermentations. Certain species produce ascospores, conidia is usually oval. 38Agaricus (Class Basidiomycetes) : The best known species is A. campestris,the field mushroom and A. bisporus ,the cultivated mushroom. Most of the larger species of Agaricus are edible.39Asp

26、ergillus (Class Deuteromycetes): the aspergilli are widespread in nature. Some species are involved in spoilage. They are used in a number of industrial fermentations, including the production of the citric acid and gluconic acid. A.niger. The aspergilli produce septate, branching mycelium. Conidia,

27、 the colors are black, brown, and green.40Penicillium (Class Deuteromycetes ): members of them occur widely in nature. Some species cause rot or other spoilage. Some are used in industrial fermentations, and penicillin is produced by P.notatum and P.chrysonegum. Some reproduce sexually by ascospore

28、formation. Penicillia have septate vegetative mycelium. 411. 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. Fungi di

29、ffer from bacteria in certain environmental requirements and in the following nutritional characteristics: 424. Fungi are capable of growing on substances with a very low moisture content, generally too low to support the growth of bacteria. 3. Most fungi are more resistant to osmotic pressures than

30、 bacteria are; most fungi are therefore able to grow in high sugar or salt concentrations. 436. Fungi are capable of using complex carbohydrates, such as lignin (wood), that most bacteria cannot metabolize. 5. Fungi require somewhat less nitrogen for growth than bacteria.444.4 yeasts Morphological c

31、haracteristics Reproduction Characteristics of colony Typical species of yeasts45Morphological characteristics Yeasts are usually unicellular. Yeast cells are larger than most bacteria.1-5um in width and 5-30 um or more in length. They are commonly egg-shaped. Yeasts have no flagella. Asexual reprod

32、uction is by budding or binary fission; Sexual reproduction is by forming ascospore.46 Saccharomyces: there are about 30 species. S.cerevisiae are used in the fermentation of beer, wine and in baking. Budding and 4 ascospores.Typical species of yeastsSchizosaccharomyces: binary fission and 8 ascospo

33、res. Some species are used in the fermentation of beer.47Life cycle of yeast484950Mushrooms are filamentous basidiomycetes that form large fruiting bodies. They live as saprophytes in the soil or on the trunks of trees. Mushroom basidospores are dispersed through the air and initiate mycelia growth

34、on favorable, usually moist, substrates. Mushrooms51From here an extensive mycelium forms following the fusion of two haploid mycelia to yield a cell containing two nuclei (a dikaryo- tic state); the latter is the beginn-ings of a fruiting body.524.5 Slime MoldsSlime molds have phenotypic similarity

35、 to both fungi and protozoa. Like fungi, slime molds undergo a life cycle and can produce spores. However, like protozoa, slime molds are motile and can move across a solid surface. 53 From a phylogenetic perspective slime molds are more ancient than fungi and some protozoa, but more derived than fl

36、agellated protozoa and their evolutio-nary predecessors. 54 The slime molds can be divided into two groups, the cellular slime molds and the acellular slime molds. For the cellular slime molds vegetative forms are composed of single amebalike cells. For acellular slime molds vegetative forms are mas

37、ses of protoplasm of indefinite size and shape called plasmodia. 55Protozoa are unicellular eukaryotic microorga-nisms that lack cell walls . They are generally colorless and motile. Protozoa are distinguished from prokaryotes by their eukaryotic nature and usually greater size, from algae by their

38、lack of chlorophyll, from yeasts and other fungi by their motility and absence of a cell wall, and from the slime molds by their lack of fruiting-body. 4.6 protozoa56Protozoa obtain food by ingesting other organ-isms or organic particles. Protozoa are found in a variety of freshwater and marine habi

39、tats; a large number are parasitic in other animals, including humans, and some are found growing in soil or in aerial habitats, such as on the surface of trees.57Most protozoa reproduce asexually, most often by binary fission. Some protozoa also exhibit sexual reproduction , usually by conjugation.

40、58Cell structure and characteristics of protozoa Protozoa are unicellular nonphotosythetic eukaryotic microorganisms and lack cell walls. Protozoans are mostly aerobic heterotrophs, although many intestinal protozoans are cap-able of anaerobic growth. Some protozoa have one nucleus, but others have

41、two or more nuclei. 59Typical species of protozoa EuglenaAmoebaParameiciumPlasmodium60Algae are a large group of eukaryotic organisms that contain chlorophyll and carry out oxygenic photosynthesis. Although most algae are of micr-oscopic size and hence are clearly microorganisms, a number of forms a

42、re macroscopic. Algae are either unicellular or colonial, the latter occurring as aggregates of cells. 4.7 Algae61Cell structure and characteristics of algae62Algae cells are eukaryotic, single cells or multicellular. Algae contain chlorophyll and are photosynthetic.Algae have a wide range of sizes

43、and sha-pes. Some colonies become quite complex and superficially resemble higher plants in structure.63The cell wall is thin and rigid, it is often surrounded by outer matrix, which often becomes pigmented and stratified. There are 5 chlorophylls: a, b, c, d, and e. Chlorophylla is present in all algae. Simple sexual reproduction or asexual reproduction (many algae produce flage-llated spores and/or non motile spores in