Biology Seventh Edition Solomon Berg Martin Chapter 23

Biology, Seventh Edition Solomon • Berg • Martin Chapter 23 Viruses and Prokaryotes Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes • Viral structure • DNA or RNA genome • Capsid –Protein coat Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes Tobacco mosaic virus Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes Adenovirus Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes T 4 bacteriophage Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 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 Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes • Origin of viruses • Escaped gene hypothesis –Viruses are often host speciesspecific –Similarity of virus genome to host genome Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 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 Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes Phages infecting E. coli bacterium Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes • Lytic cycle • Destroys the host cell –Attachment –Penetration –Replication –Assembly –Release Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes Lytic cycle Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes • Lysogenic cycle • Usually does not kill the host • Viral genome replicated along with host DNA –Attachment –Penetration –Integration –Replication Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes Lysogenic cycle Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 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 Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes Membrane Fusion Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes Endocytosis Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 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 Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 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 Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes Life cycle of HIV Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 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 Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes • Prokaryotes • No membrane-enclosed organelles such as nuclei or mitochondria Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes • Common shapes • Cocci • Bacillus (rod-shaped) • Spiral –Spirillum (rigid helix) –Spirochete (flexible helix) • Vibrios (comma shaped) Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes Micrococcus bacteria Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes Salmonella bacilli bacteria Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes Spiroplasma spirilla bacteria Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 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 Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes Gram-positive cell wall Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes Gram-negative cell wall Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 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 Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes Bacterial flagellum Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes • Genetic material • Circular DNA molecule • Plasmids • Asexual reproduction • Binary fission • Budding • Fragmentation Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes • Transformation • Intake of DNA fragments • Transduction • Phage carries bacterial DNA between cells • Conjugation • Cells of different mating types Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes Transduction Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes • Heterotrophs • Photoheterotrophs • Chemoheterotrophs –Feed on dead organic matter • Autotrophs • Photoautotrophs • Chemoautotrophs Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes • Most bacteria are aerobic • Faculatative anaerobes use oxygen if it is available • Obligate anaerobes carry on metabolism only anaerobically Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes • Domain Eubacteria • Domain Archaea • Cell walls do not have peptidoglycan • Translation mechanisms similar to eukaryotes Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes Eubacteria and Archaea Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes • Methanogens • Produce methane gas • Anaerobic environments • Extreme halophiles • Inhabit saturated salt solutions • Extreme thermophiles • Inhabit environments over 100°C Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 23 Viruses and Prokaryotes • Vital ecological functions • Decomposers • Fixing nitrogen for plants • Pathogens • Koch’s postulates • Exotoxins • Endotoxins Copyright © 2005 Brooks/Cole — Thomson Learning