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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition Solomon Berg Martin Chapter 23 Viruses and Prokaryotes
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Viral structure DNA or RNA genome Capsid –Protein coat
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Tobacco mosaic virus
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Adenovirus
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes T4 bacteriophage
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Viruses are not cells Cannot metabolize independently Forces infected host cells to replicate viral DNA Takes over cell’s translation and transcription to reproduce
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Origin of viruses Escaped gene hypothesis –Viruses are often host species- specific –Similarity of virus genome to host genome
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Origin prior to divergence of the three domains Similarities between protein structures of capsids Genetic similarities between viruses that infect the Eubacteria and the Archaea Convergent evolution unlikely
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Phages infecting E. coli bacterium
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Lytic cycle Destroys the host cell –Attachment –Penetration –Replication –Assembly –Release
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Lytic cycle
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Lysogenic cycle Usually does not kill the host Viral genome replicated along with host DNA –Attachment –Penetration –Integration –Replication
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Lysogenic cycle
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Viral infection of animal cells Surface attachment proteins bind to specific cell receptors Fuse with plasma membrane Endocytosis –Invaginates plasma membrane to form a vesicle inside the cell
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Membrane Fusion
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Endocytosis
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Viral infection of plant cells Cannot penetrate cell walls unless they are damaged Spread by insects that feed on plants or by infected seeds Spreads throughout the plant via plasmodesmata
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Retrovirus reproductive cycle Reverse transcriptase catalyzes synthesis of DNA complementary to the viral RNA Integrase integrates DNA into the host chromosome Viral DNA used to transcribe viral RNA and synthesize proteins
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Life cycle of HIV
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Viroids Short RNA strands with no protective coat Cause plant diseases Prions Only protein Cause transmissible spongiform encaphalopathies such as BSE
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Prokaryotes No membrane-enclosed organelles such as nuclei or mitochondria
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Common shapes Cocci Bacillus (rod-shaped) Spiral –Spirillum (rigid helix) –Spirochete (flexible helix) Vibrios (comma shaped)
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Micrococcus coccus bacteria
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Salmonella bacilli bacteria
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Spiroplasma spirilla bacteria
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Cell walls in eubacteria Gram-positive –Very thick peptidoglycan Gram-negative –Thin layer of peptidoglycan –Outer membrane Capsule –Surrounding the cell wall
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Gram-positive cell wall
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Gram-negative cell wall
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Pili Protein structures that extend from the cell Help bacteria adhere to surfaces Flagella Produce a rotary motion Basal body, hook, and filament
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Bacterial flagellum
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Genetic material Circular DNA molecule Plasmids Asexual reproduction Binary fission Budding Fragmentation
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Transformation Intake of DNA fragments Transduction Phage carries bacterial DNA between cells Conjugation Cells of different mating types
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Transduction
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Heterotrophs Photoheterotrophs Chemoheterotrophs –Feed on dead organic matter Autotrophs Photoautotrophs Chemoautotrophs
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Most bacteria are aerobic Faculatative anaerobes use oxygen if it is available Obligate anaerobes carry on metabolism only anaerobically
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Domain Eubacteria Domain Archaea Cell walls do not have peptidoglycan Translation mechanisms similar to eukaryotes
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Eubacteria and Archaea
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Methanogens Produce methane gas Anaerobic environments Extreme halophiles Inhabit saturated salt solutions Extreme thermophiles Inhabit environments over 100°C
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Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes Vital ecological functions Decomposers Fixing nitrogen for plants Pathogens Koch’s postulates Exotoxins Endotoxins
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