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

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

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

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

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 23 Viruses and Prokaryotes T4 bacteriophage

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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)

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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