Lecture Power Point to accompany Foundations in Microbiology

Lecture Power. Point to accompany Foundations in Microbiology Seventh Edition Talaro Chapter 5 To run the animations you must be in Slideshow View. Use the buttons on the animation to play, pause, and turn audio/text on or off. Please Note: Once you have used any of the animation functions (such as Play or Pause), you must first click in the white background before you can advance to the next slide. Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display.

5. 1 The History of Eukaryotes • They first appeared approximately 2 billion years ago • Evidence suggests evolution from prokaryotic organisms by symbiosis • Organelles originated from prokaryotic cells trapped inside them 2

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5. 2 External Structures • Locomotor appendages – Flagella • Long, sheathed cylinder containing microtubules in a 9+2 arrangement • Covered by an extension of the cell membrane • 10 X thicker than prokaryotic flagella • Function in motility – Cilia • Similar in overall structure to flagella, but shorter and more numerous • Found only on a single group of protozoa and certain animal cells • Function in motility, feeding, and filtering 7

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Figure 5. 4 Structure and locomotion in ciliates 9

External Structures • Glycocalyx – An outermost boundary that comes into direct contact with environment – Usually composed of polysaccharides – Appears as a network of fibers, a slime layer or a capsule – Functions in adherence, protection, and signal reception – Beneath the glycocalyx • Fungi and most algae have a thick, rigid cell wall • Protozoa, a few algae, and all animal cells lack a cell wall and have only a membrane 10

External Boundary Structures • Cell wall – Rigid, provides structural support and shape – Fungi have thick inner layer of polysaccharide fibers composed of chitin or cellulose and a thin layer of mixed glycans – Algae – varies in chemical composition; substances commonly found include cellulose, pectin, mannans, silicon dioxide, and calcium carbonate 11

External Boundary Structures • Cytoplasmic (cell) membrane – Typical bilayer of phospholipids and proteins – Sterols confer stability – Serves as selectively permeable barrier in transport – Eukaryotic cells also contain membrane-bound organelles that account for 60 -80% of their volume 12

5. 3 Internal Structures • Nucleus – Compact sphere, most prominent organelle of eukaryotic cell – Nuclear envelope composed of two parallel membranes separated by a narrow space and is perforated with pores – Contains chromosomes – Nucleolus – dark area for r. RNA synthesis and ribosome assembly 13

Figure 5. 5 The nucleus 14

Figure 5. 6 Mitosis 15

Internal Structures • Endoplasmic reticulum – two types: – Rough endoplasmic reticulum (RER) – originates from the outer membrane of the nuclear envelope and extends in a continuous network through cytoplasm; rough due to ribosomes; proteins synthesized and shunted into the ER for packaging and transport; first step in secretory pathway – Smooth endoplasmic reticulum (SER) – closed tubular network without ribosomes; functions in nutrient processing, synthesis, and storage of lipids 16

Figure 5. 7 Rough endoplasmic reticulum 17

Internal Structures • Golgi apparatus – Modifies, stores, and packages proteins – Consists of a stack of flattened sacs called cisternae – Transitional vesicles from the ER containing proteins go to the Golgi apparatus for modification and maturation – Condensing vesicles transport proteins to organelles or secretory proteins to the outside 18

Figure 5. 8 Golgi apparatus 19

Figure 5. 9 nucleus RER Golgi vesicles secretion 20

Internal Structures • Lysosomes – Vesicles containing enzymes that originate from Golgi apparatus – Involved in intracellular digestion of food particles and in protection against invading microbes – Participate in digestion • Vacuoles – Membrane bound sacs containing particles to be digested, excreted, or stored • Phagosome – vacuole merged with a lysosome 21

Figure 5. 10 22

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Internal Structures • Mitochondria – Function in energy production – Consist of an outer membrane and an inner membrane with folds called cristae – Cristae hold the enzymes and electron carriers of aerobic respiration – Divide independently of cell – Contain DNA and prokaryotic ribosomes 24

Figure 5. 11 Structure of mitochondrion 25

Internal Structures • Chloroplast – Convert the energy of sunlight into chemical energy through photosynthesis – Found in algae and plant cells – Outer membrane covers inner membrane folded into sacs, thylakoids, stacked into grana – Larger than mitochondria – Contain photosynthetic pigments – Primary producers of organic nutrients for other organisms 26

Figure 5. 12 27

Internal Structures • Ribosomes – Composed of r. RNA and proteins – Scattered in cytoplasm or associated with RER – Larger than prokaryotic ribosomes – Function in protein synthesis 28

Internal Structures • Cytoskeleton – Flexible framework of proteins, microfilaments and microtubules form network throughout cytoplasm – Involved in movement of cytoplasm, amoeboid movement, transport, and structural support 29

Figure 5. 13 A model of the cytoskeleton 30

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Survey of Eukaryotic Microbes • • Fungi Algae Protozoa Parasitic worms 33

5. 4 Kingdom Fungi • 100, 000 species divided into 2 groups: – Macroscopic fungi (mushrooms, puffballs, gill fungi) – Microscopic fungi (molds, yeasts) – Majority are unicellular or colonial; a few have cellular specialization 34

Microscopic Fungi • Exist in two morphologies: – Yeast – round ovoid shape, asexual reproduction – Hyphae – long filamentous fungi or molds • Some exist in either form – dimorphic – characteristic of some pathogenic molds 35

Figure 5. 15 36

Figure 5. 16 c 37

Fungal Nutrition • All are heterotrophic • Majority are harmless saprobes living off dead plants and animals • Some are parasites, living on the tissues of other organisms, but none are obligate – Mycoses – fungal infections • Growth temperature 20 o-40 o. C • Extremely widespread distribution in many habitats 38

Figure 5. 17 Nutritional sources for fungi 39

Fungal Organization • Most grow in loose associations or colonies • Yeast – soft, uniform texture and appearance • Filamentous fungi – mass of hyphae called mycelium; cottony, hairy, or velvety texture – Hyphae may be divided by cross walls – septate – Vegetative hyphae – digest and absorb nutrients – Reproductive hyphae – produce spores for reproduction 40

Figure 5. 18 41

Fungal Reproduction • Primarily through spores formed on reproductive hyphae • Asexual reproduction – spores are formed through budding or mitosis; conidia or sporangiospores 42

Figure 5. 19 43

Fungal Reproduction • Sexual reproduction – spores are formed following fusion of two different strains and formation of sexual structure – Zygospores, ascospores, and basidiospores • Sexual spores and spore-forming structures are one basis for classification 44

Figure 5. 20 Formation of zygospores 45

Figure 5. 21 Production of ascospores 46

Figure 5. 22 Formation of basidiospores in a mushroom 47

Fungal Classification Kingdom Eumycota is subdivided into several phyla based upon the type of sexual reproduction: 1. Zygomycota – zygospores; sporangiospores and some conidia 2. Ascomycota – ascospores; conidia 3. Basidiomycota – basidiospores; conidia 4. Chytridomycota – flagellated spores 5. Fungi that produce only Asexual Spores (Imperfect) 48

Fungal Identification • Isolation on specific media • Macroscopic and microscopic observation of: – Asexual spore-forming structures and spores – Hyphal type – Colony texture and pigmentation – Physiological characteristics – Genetic makeup 49

Roles of Fungi • Adverse impact – Mycoses, allergies, toxin production – Destruction of crops and food storages • Beneficial impact – Decomposers of dead plants and animals – Sources of antibiotics, alcohol, organic acids, vitamins – Used in making foods and in genetic studies 50

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5. 5 Kingdom Protista • Algae - eukaryotic organisms, usually unicellular and colonial, that photosynthesize with chlorophyll a • Protozoa - unicellular eukaryotes that lack tissues and share similarities in cell structure, nutrition, life cycle, and biochemistry 52

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Algae • Photosynthetic organisms • Microscopic forms are unicellular, colonial, filamentous • Macroscopic forms are colonial and multicellular • Contain chloroplasts with chlorophyll and other pigments • Cell wall • May or may not have flagella 54

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Algae • Most are free-living in fresh and marine water – plankton • Provide basis of food web in most aquatic habitats • Produce large proportion of atmospheric O 2 • Dinoflagellates can cause red tides and give off toxins that cause food poisoning with neurological symptoms • Classified according to types of pigments and cell wall • Used for cosmetics, food, and medical products 56

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Protozoa • • • Diverse group of 65, 000 species Vary in shape, lack a cell wall Most are unicellular; colonies are rare Most are harmless, free-living in a moist habitat Some are animal parasites and can be spread by insect vectors • All are heterotrophic – lack chloroplasts • Cytoplasm divided into ectoplasm and endoplasm • Feed by engulfing other microbes and organic matter 58

Protozoa • Most have locomotor structures – flagella, cilia, or pseudopods • Exist as trophozoite – motile feeding stage • Many can enter into a dormant resting stage when conditions are unfavorable for growth and feeding – cyst • All reproduce asexually, mitosis or multiple fission; many also reproduce sexually – conjugation 59

Figure 5. 27 60

Protozoan Identification • • Classification is difficult because of diversity Simple grouping is based on method of motility, reproduction, and life cycle 1. Mastigophora – primarily flagellar motility, some flagellar and amoeboid; sexual reproduction 2. Sarcodina – primarily amoeba; asexual by fission; most are free-living 3. Ciliophora – cilia; trophozoites and cysts; most are freeliving, harmless 4. Apicomplexa – motility is absent except male gametes; sexual and asexual reproduction; complex life cycle – all parasitic 61

Figure 5. 28 62

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Important Protozoan Pathogens • Pathogenic flagellates – Trypanosoma • T. brucei – African sleeping sickness • T. cruzi – Chaga’s disease; South America • Infective amoebas – Entamoeba histolytica – amebic dysentery; worldwide 66

Figure 5. 32 67

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Parasitic Helminths • Multicellular animals, organs for reproduction, digestion, movement, protection • Parasitize host tissues • Have mouthparts for attachment to or digestion of host tissues • Most have well-developed sex organs that produce eggs and sperm • Fertilized eggs go through larval period in or out of host body 70

Major Groups of Parasitic Helminths 1. Flatworms – flat, no definite body cavity; digestive tract a blind pouch; simple excretory and nervous systems • Cestodes (tapeworms) • Trematodes or flukes, are flattened, nonsegmented worms with sucking mouthparts 2. Roundworms (nematodes) – round, a complete digestive tract, a protective surface cuticle, spines and hooks on mouth; excretory and nervous systems poorly developed 71

Helminths • Acquired through ingestion of larvae or eggs in food; from soil or water; some are carried by insect vectors • Afflict billions of humans 72

Figure 5. 34 Parasitic Flatworms 73

Figure 5. 35 74

Helminth Classification and Identification • Classify according to shape, size, organ development, presence of hooks, suckers, or other special structures, mode of reproduction, hosts, and appearance of eggs and larvae • Identify by microscopic detection of adult worm, larvae, or eggs 75

Distribution and Importance of Parasitic Worms • Approximately 50 species parasitize humans • Distributed worldwide; some restricted to certain geographic regions with higher incidence in tropics 76