1、Chapter 19 The Diversity of Viruses, Prokaryotes, and Protists,炭疽病(Anthrax)& 炭疽桿菌(Bacillus anthracis),Normal : goat and sheep not human weaponized 耗氧性 革蘭氏陽性桿菌 耐熱孢子,2001 Washington, D.C. Harmless envelope,19.1 What Are Viruses, Viroids, and Prions?,19.1.1 A Virus Consists of a Molecule of DNA or RNA
2、Surrounded by a Protein Coat,No membranes ribosomes cytoplasm source of energy Viruses replicate inside host cells using the replication machinery of the host cell.,Eukaryotic cells (10100 m),Prokaryotic cells (0.210 m),cyanobacterium,Viruses (0.050.2 m),Escherichia coli,Staphylococcus,1 m,glycoprot
3、eins,protein coat,envelope (lipid bilayer),spikes,core proteins,reverse transcriptase,genetic material (viral RNA) coated with protein,Two major parts: A molecule of hereditary material -DNA or RNAsingle-stranded or double-stranded- template for the viral proteins and genetic material 2. a coat of p
4、rotein surrounding the molecule- is specialized to enable the virus to penetrate the cells of a specific host,glycoproteins,protein coat,envelope (lipid bilayer),spikes,core proteins,reverse transcriptase,genetic material (viral RNA) coated with protein,Why are viruses unable to replicate outside of
5、 a host cell?,Viruses Are Host-Specific,Host-specific:Each type of virus is specialized to attack a specific host cells No organism is immune to all viruses,Bacteriophage,Viruses that infect bacteria Treatment of the patients infected by bacteria with bacteriophage Advantages: Bacteria become increa
6、singly resistant to antibiotics Host specificity Harmless to beneficial bacteria,bacteriophages are seen attacking a bacterium. They have injected their genetic material inside, leaving their protein coats clinging to the bacterial cell wall. The black objects inside the bacterium are newly forming
7、viruses.,Viruses for animals and plants,Virus respiratory tract cold skin measles麻疹 Rabies virus nerve(狂犬病) Herpes mucous membranes of mouth, lips, genitals Permanent residence Erupting periodically HIV AIDS through attaching T cells,rabies virus,herpes virus,bacteriophage,tobaccomosaic plant virus,
8、measles virus,Copyright 2005 Pearson Prentice Hall, Inc.,Viral replication,Five steps: Penetration replication Transcription Protein synthesis Viral assembly Release,(nucleus),DNA,RNA,mRNA,(cytoplasm),RNA,core,envelope,coat,reverse transcriptase,HIV virus, a retrovirus, invades a white blood cell.,G
9、P120 receptors T4 cells (cd4 receptors ),mRNA,DNA,(cytoplasm),(nucleus),Herpes virus, a double-stranded DNA virus, invades a skin cell.,Viral infections are difficult to treat,No Antibiotics Antiviral agentsdestroy host cells as well Antiviral drugs Destroy or block the function of Enz that the targ
10、et virus required for replication Mutation of viruses against drugs Biological weapons Smallpox Ebola hemorrhagic fever伊波拉病毒出血熱,19.1.2 Some Infectious Agents Are Even Simpler Than Viruses,Viroids: infectious particles but lack protein coat short circular strands of RNA enter nucleus and direct the s
11、ynthesis of new viroids Many crop diseases Prions: Puzzling proteins,Prions,Creutzfeldt-Jakob disease (庫賈氏病)及kuru (克魯症)，bovine spongiform encephalopathy(狂牛症)、及scrapie(羊搔癢症,在羊身上）、貂腦症（在貂身上） Spongiform in their brain tissue Can be inherited as well as transmitted by infection Stanley Prusiner (1982 Nob
12、el Prize Winner),Prions: Puzzling proteins,No one is certain how these infectious particles originated,Evolutionary remnants The degenerate descendants of parasitic cells,Bacteria and Archaea domains,Consist entirely of prokaryotes Single-celled microbes that lack organelles Very small (ranging from
13、 about 0.2 to 10 m in diameter) Bacteria and Archaea Are fundamentally Different In both their structural and biochemical features Differ in structure, composition of cell wall, plasma membrane, ribosomes, RNA polymerase, transcription and translation process,Classification basis of prokaryotes,Shap
14、e Means of locomotion Pigments Nutrients requirements The appearance of colonies The staining properties Gram stain (distinguishes two types of cell wall construction in bacteria) Gram-positive or gram-negative,Classification based on nucleotide sequence,Comparisons of DNA and RNA sequences Bacteria
15、 13-15 kingdoms Archaea 3 kingdoms,Notes on Classification of prokaryotes,is a rapidly changing field consensus on kingdom-level classification has proved elusive thus far,New DNA sequences data,New and distinctive types of bacteria and archaea being discovered and described on a regular basis,Proka
16、ryote classification schemes will likely continue to be dynamic for some time to come,Prokaryotes Differ in Shape and Structure,Common shapes rodlike, spherical, corkscrew-shaped Flagella (Figure 19-7) Protective slime layers (some bacteria) (Figure 19-8) Protective slime Composed of polysaccharides
17、 and protein Biofilmsslime-secreting bacteria of one or more species aggregate in colonies to form communities known as,0.10 m,0.25 m,outer membrane,peptidoglycan layer,plasma membrane,cell wall,“wheel-and- axle” base,(b),The prokaryote flagellum 1. Singly 2. In pairs 3. As a tuft 4. Scattered,Many
18、Bacteria Form Films on Surfaces,Endospores,Protective structure inside a bacterium Allow Some Bacteria to Withstand Adverse Conditions Extreme conditions Time (spores sealed inside rock for 250 million yrs) Contains genetic material and a few enzymes encased within a thick protective coat Metabolic
19、activity ceases until the spore encounters favorable conditions,endospore,bacterium,Resistant endospores have formed inside bacteria of the genus Clostridium, which causes the potentially fatal food poisoning called botulism. 肉毒桿菌中毒,Reproduce asexually Divide every 20 min, 1021 in one day,Prokaryote
20、s reproduce by binary fission,Prokaryotes may exchange genetic material without reproducing,Conjugation - prokaryotic mating,Sex pili,Plasmids,A small circular DNA molecule that is separate from the single bacterial chromosome Carry genes for Antibiotic resistance conjugation Alleles of Chromosomal
21、genes,Prokaryotes Are Specialized for Specific Habitats,Prokaryotes occupy virtually every habitat Some prokaryotes thrive in extreme conditions Temperature110oC or in Antarctic sea Pressure - 2.8 km below earth surface Salinity Dead sea Various locations in humans Most prokaryotes are specialists (
22、specialized),Hot springs harbor bacteria and archaea that are both heat- and mineral-tolerant.,Prokaryotes Exhibit Diverse Metabolisms,Oxygen Anaerobes Many archaea found in hot springs and bacterium that cause tetanus Opportunists AerobesEnergy source: organic compounds : petroleum, methane, benzen
23、e, toluene Inorganic compds: hydrogen, sulfur, ammonia, iron, and nitrite Photosynthetic bacteria like cyanobacteria Possess chlorophyll Sulfur bacteria Hydrogen sulfide instead of water using in photosynthesis No photosynthetic Archaea are known,membranes bearing chlorophyll,Chlorophyll is located
24、on the membranes visible within the cells.,Cyanobacteria藍綠菌,Prokaryotes Perform Functions Important to Other Organisms,Cellulose digesters for many leaf eaters Food industry for cheese, yogurt Humans food products and vitamins K and B12 Nitrogen-fixing bacteria (Figure 19-14) in soil, in root nodule
25、s (p. 370) Recyclers biodegradation and decomposition Biodegradable,cell walls,N2-fixing bacteria,Some Bacteria Pose a Threat to Human Health,Pathogenic (disease-producing) Some Anaerobic Bacteria Produce Dangerous Poisons- Botulism, tetanus bacteria through wound, Humans Have Battled Bacterial Dise
26、ases Black Death Yersinia pestis 感染的齧齒類動物由跳蚤傳染給人類 Lyme arthritis (萊姆症、萊姆關節炎) Borrelia burgdorferi by deer ticks Some Common Bacterial Species Can Be Harmful Most Bacteria Are Harmless,19.3 What Are Protists?,Protist means:Any eukaryote that is not a plant , animal, or fungus 60,000 protist species T
27、able 19.1 The Major Groups of Protists (p. 372) Most protists are single-celled Visible and invisible (naked eye),Reproduction of protists,Reproductive process Asexually by mitotic cell division Sexual reproduction No embryo development Nonreproductive process Combine the genetic material of differe
28、nt individuals,reproduces asexually by cell division.,exchanges genetic material across a cytoplasmic bridge,Protists Use Diverse Modes of Nutrition,Three major modes: Photosynthetic protists: solar energy Predatory protists : ingest food Parasitic protists : absorb nutrients from their surroundings
29、 Past classification was according to the nutrition need of protists Algae: photosynthetic protists Protozoa : single-celled, nonphotosynthetic protists Protists systematics are in transition,The Chromists,Form a group (a kingdom by some systematists) whose shared ancestry was discovered through gen
30、etic comparison Have fine, hairlike projections on their flagella In many, flagella are present only at certain stages of the life cycle Display a wide range of different forms Photosynthetic or nonphotosynthetic Single-celled or multicellular Three major groups are: Water molds Diatoms Brown algae,
31、Water Molds,Oomycetes (Small group of protists) Shaped as long filaments that aggregate to form cottony tufts Similar to fungus Decomposers live in water and damp soil Some are pathogenic Downy mildew on grapes Late blight Potato late blight avocado鱷梨trees in California,A parasitic water mold, Downy
32、 mildew, a plant disease caused by the water mold Plasmopara, nearly destroyed the French wine industry in the 1870s.,Diatoms,Photosynthetic chromists found in both fresh and salt water Form part of the Phytoplankton Marine phytoplankton account for 70% photosynthetic activity on earth Pastures of t
33、he sea Produce protective shells of silica Consist of top and bottom halves Accumulation of shells produce diatomaceous earth Used in products such as toothpaste and metal polish,Brown Algae,Seaweeds multicellular aggregation Marine Dominate in Cool Coastal Waters Contain Brown yellow pigments / gre
34、en chlorophyll Increase their light gathering ability Several species us gas-filled floats to support the bodies,Brown algae, a multicellular protistGiant kelp Macrocystis Height of 100 meters and may grow more than 15 cm/day,The Alveolates,Are single-celled organisms that have distinctive cavities
35、beneath the surface of their cells Show a variety of structures and ways of life Photosynthetic Parasitic predatory They were revealed as a group by molecular comparison The major groups are: Dinoflagellates Apicomplexans Ciliates,Dinoflagellates,Contain two whiplike flagella One encircles the cell
36、Second projects behind it Most are photosynthetic Some are enclosed only by a membrane, others have cellulose walls Especially abundant in the ocean (also live in fresh water) important component of phytoplankton Bioluminescentblue green light Specialized dinoflagellates live within the tissues of c
37、orals, some clams, and even other protists,Two dinoflagellates covered with protective cellulose armor. Visible on each is a flagellum in a groove that encircles the body.,The explosive reproductive rate of certain dinoflagellatesRed tide fish die (depletion of oxygen or suffocated by clogged gills)
38、Dinoflagellate Pfisteria eat fish by secreting chemicals that dissolve the victims fleshBenefit oyster, mussels and clams accumulate Nerve poison produced by the dinoflagellates,Apicomplexans,Known as sporozoans Are Parasitic They form infectious spores resistant structure transmitted from one host
39、to another through food, water, or the bite of an infected insect As adults, have no means of locomotion Many have complex life cycles Malarial parasite Plasmodium Chloroquine Drug resistant,(in mosquito),(in human),male gamete,female gamete,saliva with larvae are injected into human,larvae migrate
40、to salivary gland,larvae develop,larvae enter liver; develop through several larval stages,parasites emerge from liver and enter red blood cells,liver,some parasites become gametocytes,male gametocyte,female gametocyte,synchronized rupture of red blood cells, releasing the parasites and toxins, caus
41、es the recurring fever of malaria,parasites reproduce in red blood cells, which burst, liberating new parasites that infect more red blood cells,female Anopheles mosquito bites human and ingests gametocytes, which become gametes,fertilization produces a zygote that enters the wall of the mosquitos s
42、tomach,Ciliates,Inhabit fresh and salt water Represent the peak of unicellular complexity Possess many specialized organelles Cilia May cover the cell or may be localized Paramecium 草履蟲 Cilia cover the organisms entire body surface Coordinated beating propels the cell through the water at a rate of
43、one millimeter per second Didinium ciliates , predator,macronucleus,oral groove,food vacuole forming,cilia,contractile vacuole,anal pore,food vacuole,micronucleus,Copyright 2005 Pearson Prentice Hall, Inc.,Didinium attacks a Paramecium,Slime Molds,Distinctive protist lineage that could become its ow
44、n kingdom when a consensus on eukaryote classification Physical form : seems to blur the boundary between a colony of different individuals and a single, multicellular individual Are Decomposers That Inhabit the Forest FloorThe life cycle of slime mold consists of two phases: A mobile feeding stage
45、A stationary reproductive stage called a fruiting bodyTwo types of slime mold Acellular Cellular,Acellular Slime Molds,Or plasmodial slime molds Consists of a mass of cytoplasm that may spread thinly over an area of several square meters. Contains thousands of diploid nuclei, the nuclei are not conf
46、ined in separate cells surrounded by plasma membranes-form a multinucleate mass of cytoplasm This structure is called plasmodium (acellular),Dry conditions or starvation stimulate the plasmodium form a fruiting bodyOn which haploid spores are produced,Cellular Slime Molds,Live in soil as independent
47、 haploid cells Move and feed by pseudopods Dictyostelium When food becomes scarce Release a chemical signal Attracts nearby cells into a dense aggregation that forms a sluglike mass-pseudoplasmodium Behaves like a multicellular organsism Crawling toward a source of light Forming a fruiting body Hapl
48、oid spores formed,nucleus,spores,fruiting bodies,cAMP,Euglenoids,Single-celled protists Live mostly in fresh water and are named after the best-known representative -Euglena Photosynthetic Possess simple light-sensing organelles consisting of a photoreceptor-eyespot Lack a rigid covering and swim by
49、 means of Flagella,flagellum,eyespot,contractile vacuole,stored food,nucleus,nucleolus,chloroplasts,Red Algae,Multicellular, photosynthetic seaweeds Colored from bright red to nearly black Absorb blue-green light than transfer the energy to chlorophyll (photosynthesis) Exclusively found in marine environments Live primarily in clear tropical oceans Some species of red algae deposit calcium carbonate, which forms limestone, in their tissues and contribute to the formation of reefs Red algae Gelatinous substances with commercial uses agar,
