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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 and protein Biofilmsslime-secreting bacteria of one or more species aggregate in colonies to form communities known as,
