Chapter II Eukarya: Eukaryotic Microorganisms Algae: Phototrophic eukaryotic microorganisms Fungi: Non-photosynthetic eukaryotic microorganisms that contain rigid cell walls Slime molds: nonphototrophic eukaryotic microorganisms that lack cell walls and that aggregate to form fruiting structures (cellular slime molds) or masses of protoplasm (acellular slime molds) Protozoa: unicellular eukaryotic microorganisms that lack cell walls

Seveal concepts Mycologists: scientists who study fungi Mycology: the scientific discipline dealing with fungi. Mycotoxixology: the study of fungal toxins and their effects. Mycosis/mycoses: the diseases caused by fungi in animals.

Importance of fungi 1. decomposers 2. Major cause of plant diseases 3. Many diseases of animals and humans are caused by fungi 4. products: the making of bread, wine, beer(yeasts); the preparation of some cheeses, soy sauce and sufu; the commercial production of many organic acids and certain drugs; The manufacture of many antibiotics and immunosuppressive drug cyclosporine. 5. Important research tools in the study of fundamental biological processes.

Fungi: Molds, Yeasts and Mushrooms Habitats diverse: aquatic in fresh water or marine, terrestrial in soil or on dead plant, a few are human parasitic Have rigid cell walls (resemble plant cell walls architecturally, not chemically) containing chitin (some with mannans, galactosans, chitosans instead of chitin) Fungal cell walls are 80-90% polysaccharide, with proteins, lipids, polyphosphates and inorganic ions making up the wall-cementing matrix

Thallus : the body or vegetative structure of a fungus. Hypha (hyphae) : long, branched, threadlike filament Mycelium: a tangled mass or tissuelike aggregation Coenocytic: hyphae that protoplasm streams through hyphae, uninterrupted by cross walls. Septate: the hyphae have cross walls called septa with either a single pore or multiple pores that permit cytoplasmic streaming. (Septa: cross walls with either a single pore or multiple pores that permit cytoplasmic streaming.)

YM shift Many fungi that cause diseases in humans and animals, are dimorphic: they have two forms. 1. The yeast (Y) form in the animals 2. The mold or mycelial form (M) in the external enviroments. Plant-associated fungi: the mycelial form in the plant the yeast form in the external environment.

yeasts Unicellular fungus, spherical to egg shaped, single nucleus and reproduces either asexually by budding and transverse division or sexually through spore formation No flagella, possess most of the other eucaryotic organelles..

Yeasts: unicellular fungi (ascomycetes) Division: budding Do not form filaments Some form filaments Some can mate.

Cillia and flagella Both are associated with motility. Both are whip like and beat to move the microorganism along Difference: 1.cilia are typically only 5 to 20  m in length, whereas flagella are 100 to 200  m long. 2. Distinctive movement patterns: flagella: move in an undulating fashion and generate planar or helical waves originating at either the base or the tip. cillia:like an oar.

Cilia and flagella structure Fig4.24p90

Colony

Eucaryotic cell structure

The Nucleus The nucleus is both a storehouse and a processing factory for genetic information. The process of protein synthesis occurs in the cytoplasm

Chromosomes and DNA Histones are spaced along the DNA double helix at regular intervals, the DNA itself being wound around each histone molecule. The packing forms a discrete structure called a nucleosome. Nucleosomes aggregate and form a fibrous material called chromatin. Chromatin itself can be compacted by folding and looping to eventually form an intact chromosome

Mitosis ( 有丝分裂 ) During cell division, the nucleus divides following a doubling of the chromosome number, a process called mitosis, yielding two cells, each with a full complement of chromosome. Metaphase: chromosomes are paired in the center of the cell. Anaphase: chromosomes are separating.

Organelles: Mitochondria and Chloroplasts Eukaryotic cells have a number of important functions localized in discrete bodies called organelles: Mitochondria: in which energy metabolism is carried out, Chloroplasts:in which the process of photosynthesis is carried out in plants and algae.

Structure of the mitochondrion A bilayer of phospho- lipid with embedded proteins. Cristae( 脊 ): sites of enzymes involved in respiration and ATP production and of specific transport proteins that regulate the passage of metabolites into and out of the matrix of the mitochondrion. Matrix( 基质 ) ： contains a number of enzymes involved in the oxidation of organic compounds (TCA cycle).

Structure of the chloroplasts Thylakoids( 类囊体 ):the thylakoid membrane is highly impermeable to ions and other metabolites because its function is to establish the proton motive force necessary for ATP synthesis.

Detailed structure of the chloroplasts Stroma contains large amounts of the enzyme ribulose bisphosphate carboxylase (RubisCO) that convert CO2 to organic form.

Relationships of organelles to bacteria It was suggested that mitochondria and chloroplasts are descendents of ancient prokaryotic organisms. Endosymbiosis theory: Eukaryotes arose from the engulfment of a prokaryotic cell by a large cell. Evidences: Mitochondria and chloroplasts contain DNA, Mitochondria and chloroplasts contain their own ribosomes Antibiotic specificity Phylogeny

Asexual spores Arthroconidia: by the separation of hyphae through splitting of the cell wall or septum to form cells that behave as spores. Chlamydospores: the cells are surrounded by a thick wall before separation. Sporangiospores: the spores develop within a sporangium (sac) at a hyphal tip. Conidiospores: the spores are not enclosed in a sac but produced at the tips or sides of the hypha. Blastospores: spores produced from a vegetative mother cell by budding.

Molds: filamentous fungi Conidia: asexual spores, pigmented, resistant to drying

Comparison of prokaryotic and eukaryotic cells Table 3-5 p62

Questions What are Eukaryotic Microorganisms Several concept Importance of fungi YM shift The character and reproduction of yeast Special style of mycelium Cillia and flagella The feature of colony Eucaryotic cell structure The reproduction of fungi Comparison of procaryotic and eukaryotic cells

Classification of Fungi Based on –morphological properties –sexual life cycles

子囊菌 担子菌 接合菌 卵菌 半知菌 多核的