topiceukaryoticmicrobes

1、Eukaryotic MicroorganismsChapter outline2.1 Eukaryotic cell structure2.2 Fungal growth and reproduction2.3 Major group and properties of fungi2.4 Yeasts2.5 Slime molds（粘菌类）2.6 Protozoa（原生动物）2.7 Algae (藻类） Concepts Eukaryotes, genetic material is distributed between cells by the highly organized , co

2、mplex 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(异养的) microorganism

3、s.2.1 Eukaryotic cell structureCytoplasmicmembraneRibosomesCytoplasmMitochondrionNuclear membraneNucleusNucleolusEndoplasmicreticulumChloroplastThe 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 ma

4、y be absent . Organelles are universal among eukaryotic cells while chloroplasts are found only in photosynthetic cells. Molds Mushrooms Fungi Yeasts Algae Protozoa Eukaryotic MicroorganismsMajor differences among fungi, algae and protozoansFUNGIALGAEPROTOZOANSKingdomFungiProtista and PlanteeProtist

5、aNutritional typeChemoheterotrophPhotoautotrophChemoheterotrophMulticellularAll, except yeastsSome None Cellular arrangement Unicellular, filamentous, fleshy(such as mushrooms)Unicellular, colonial, filamentous, tissuesUnicellular Food acquisitionAbsorptive Absorptive Absorptive cytostomeCharacteris

6、tic featureSexual and asexual sporesPigments Motility; some form cysts Embryo None Some None Protozoa are animallike protists exhibiting heterotrophic nutrition and they can be def- ined as usually motile eukaryotic unicellular microorganisms.Fungi are heterotrophic eukaryotic microorga- nisms. They

7、 are nonphotosynthetic and typically form reproductive spores.Algae are phototrophic eukaryotes that contain photosynthetic pigments within a structure called the chloroplastFungi contain cell walls and produce spores, most described species form a relatively tight phylogenetic cluster.the moldsthe

8、yeasts the mushrooms2.2 Fungal growth and reproduction Three major groups of fungi are recognized:The molds are filamentous fungi. They are widespread in nature. Each filament grows mainly at the tip, by extension of the terminal cell . Molds A single filament is called a hypha (plural, hyphae). Hyp

9、hae usually grow together across a surface and form compact tufts, collectively called a mycelium, which can be seen easily without a microscopeIn most 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,

10、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 move.Mycelium.swf(1)nonseptate(2)septaten The morphology n Reproductionn Classification n Typical species Filamentous fungiThe morphology of filament

11、ous 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 cytoplasmic movement within a hypha, generally in a direc-tion toward the hyphal tip, and the older portions of the hypha usually bec

12、ome vacuolated and virtually devoid of cytoplasm. Each hypha is about 5-10 um wide.ReproductionAsexual spores are formed by the aerial mycelium of one organism. When these spores germinate, they become organisms that are genetically identical to the parent. Sexual spores result from the fusion of nu

13、clei from two opposite mating strains of the same species of fungus. Organisms that grow from sexual spores will have genetic characteristics of both parental strains.Asexual spores are produced by an individual fungus through mitosis and subsequent cell division; there is no fusion of the nuclei of

14、 cells. Several types of asexual spores are produced by fungi. Asexual SporesMain types of asexual sporesnSporangiospores sprndisp:孢囊孢子孢囊孢子Conidiospores kunidisp: 分生孢子Arthrospores :rsp: 分节孢子分节孢子nChlamydospores klmidsp: 厚垣孢子厚垣孢子nZygospore zaisp: 接合孢子接合孢子Sporangiospores Sporangiospores are formed with

15、in a sporangium Rhizopus (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 present.T2010.gifrhizoidSporangiospores Chlamydo

16、spores are thick-walled cells within the hyphae ChlamydosporesArthrospores节孢子（arthrospore）又称粉孢子（oidium），其形成过程是菌丝生长到一定阶段，菌丝上生出许多横隔，然后从分隔出断裂，产生许多形状如短柱状、筒状或两端呈钝圆形的节孢子。ConidiosporesConidiospores are arranged in chains at the end of a conidiophore ConidiosporesName of fungus Location of spores ExamplesCh

17、lamydosporeExternalMucor racemosusArthrosporeExternalGeotrichum candidumConidiospore ExternalAspergillus nigerPenicillium notatumSporangiospore InternalRhizopus oryzaeAsexual spores of filamentous fungiSome molds also produce sexual spores, formed as a result of sexual reproduction. The latter occur

18、 from the fusion either of unicellular gametes or of specialized hyphae called gametangia(配子囊). 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 Spores1. A haploid nucl

19、eus of a donor cell (+) penetrates the cytoplasm of a recipient cell (Plasmogamy，胞质融合).2. The (+) and (-) nuclei fuse to form a diploid zygote nucleus (Karyogamy，核融合).3. By meiosis, the diploid nucleus gives rise to haploid nuclei (sexual spores), some of which may be genetic recombinants (Meiosis，减

20、数分裂).A fungal sexual spore results from sexual reproduction, consisting of three phases:Several types of sexual sporesn Oospores（卵孢子）n Zygospores（接合孢子）n Ascospores （子囊孢子）n Basidiospores （担孢子）Oospores formed within a special female structure, the oogonium. Fertilization of eggs, or oospheres, by male

21、 gametes in an antheridium give rise to oospores.Antheridium，雄器Oospheres，卵球oosporesOogonium，藏卵器Oospores formationZygospores are large, thick-walled spores formed when the tips of two sexually compatible hyphae of certain fungi fuse together. ZygosporesZygosporesAscospores are single-celled ,they are

22、 produced in a sac called an ascus（子囊）. There are usually 8 ascospores in each ascus.Various ascocarps（子囊果） formed by different ascomycete fungi（子囊菌）.plectocarppyrenocarpdiscocarpAscosporesBasidiospores are single-celled spores, they are borne on a club-shaped structure called basidium（担子）.Basidiosp

23、oresClassification of fungin The classification of fungi is based primarily on the characteristics of the sexual spores and fruiting bodies present during the sexual stages of their life cycles.n The perfect life cycle of many fungi are yet unknown. They are placed in a special class of Deuteromycet

24、es(半知菌)Typical species of filamentous fungiMucor ，毛霉(class Zygomycetes接合菌亚纲): occur in soil and on fruits, vegetables and starchy foods. Some 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 pres

25、ent. No stolons（匍匐枝） or rhizoids.Rhizopus (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 present.Neurospora（链孢霉属） (Class

26、 Ascomycetes子囊菌纲) : this genus is widely used in the study of genetics and metabolic pathways. Some species are responsible for food spoilage, and some species are used in industrial fermentations. Certain species produce ascospores, conidia is usually oval. Agaricus（伞菌属） (Class Basidiomycetes担子菌纲)

27、: 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.Mushrooms are filamentous basidiomycetes that form large fruiting bodies. They live as saprophytes（腐生物） in the soil or on the trunks of trees. Mush

28、room basidospores are dispersed through the air and initiate mycelia growth on favorable, usually moist, substrates. MushroomsFrom 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

29、of a fruiting body.Penicillium (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 （点青霉）and P.chrysonegum. Some reproduce sexually by ascospore formation. Penicil

30、lia have septate vegetative mycelium. 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 （兼性厌氧生物）. Fungi differ from b

31、acteria 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. 3. Most fungi are more resistant to osmotic pressures than bacteria are

32、; most fungi are therefore able to grow in high sugar or salt concentrations. 6. 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.2.4 yeastsn Morphological characteristics n

33、 Reproductionn Characteristics of colony n Typical species of yeastsMorphological characteristicsn 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. n Asexual reproduction is

34、by budding or binary fission; Sexual reproduction is by forming ascospore.n Saccharomyces（酵母属）: 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 yeastsnSchizosaccharomyces（裂殖酵母属）: binary fission and 8 ascos

35、pores. Some species are used in the fermentation of beer.2.5 Slime Molds粘液菌类Slime molds have phenotypic similarity 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. From

36、 a phylogenetic perspective slime molds are more ancient than fungi and some protozoa, but more derived than flagellated protozoa and their evolutionary predecessors. The slime molds can be divided into two groups, the cellular slime molds and the acellular slime molds. For the cellular slime molds

37、vegetative forms are composed of single amebalike cells. For acellular slime molds vegetative forms are masses of protoplasm of indefinite size and shape called plasmodia（原质团，原形体，疟原虫）. Protozoa are unicellular eukaryotic microorga-nisms that lack cell walls . They are generally colorless and motile.

38、 Protozoa are distinguished from prokaryotes by their eukaryotic nature and usually greater size, from algae by their 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. 2.6 protozoaProtozoa obtain fo

39、od by ingesting other organ-isms or organic particles. Protozoa are found in a variety of freshwater and marine habitats; 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.Most protozoa reproduce

40、 asexually, most often by binary fission. Some protozoa also exhibit sexual reproduction , usually by conjugation.Cell structure and characteristics of protozoan Protozoa are unicellular nonphotosythetic eukaryotic microorganisms and lack cell walls. n Protozoans are mostly aerobic heterotrophs, alt

41、hough many intestinal protozoans are cap-able of anaerobic growth. n Some protozoa have one nucleus, but others have two or more nuclei. Typical species of protozoa Euglena 眼虫藻Amoeba变形虫Parameicium 草履虫Plasmodium疟原虫Algae are a large group of eukaryotic organisms that contain chlorophyll and carry out

42、oxygenic photosynthesis. Although most algae are of micr-oscopic size and hence are clearly microorganisms, a number of forms are macroscopic（肉眼可见的）. Algae are either unicellular or colonial, the latter occurring as aggregates of cells. 2.7 AlgaeCell structure and characteristics of algaenAlgae cells are eukaryotic, single cells or multicellular. Algae contain chlorophyll and are photo