Bio 100 Chapter 16

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Bio 100 Chapter 16

  1. 1. Chapter 16 Evolution of Microbial Life Lecture OutlineCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  2. 2. 16.1 Viruses have a simple structure Viruses are noncellular /nonliving Size comparable to large protein macromolecule  Ranging from 0.2 to 2 μm Basic anatomy of a Virus  Outer capsid composed of protein  May be surrounded by outer membranous envelope  Inner core of nucleic acid (DNA or RNA) 16-2
  3. 3. Figure 16.1A Adenovirus, a naked virus, with a polyhedral capsid anda fiber at each corner Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. capsid fiber DNA protein unit TEM 80,000× (Right): © Dr. Hans Gelderblom/Visuals Unlimited 16-3
  4. 4. Figure 16.1B Influenza virus, surrounded by an envelope with spikes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. spike RNA envelope capsid 20 nm (Right): © K.G. Murti/Visuals Unlimited 16-4
  5. 5.  Classification of Viruses: 1. Their type of nucleic acid – DNA or RNA 2. Whether nucleic acid is single-stranded or double-stranded 3. Size and shape 4. Presence or absence of an outer membrane 16-5
  6. 6. 16.2 Some viruses reproduce inside bacteria Bacteriophages (phages)  Viruses that infect bacteria  Two types of life cycles  Lytic cycle  Most common  5 stages  Lysogenic cycle  Phage becomes latent – called prophage  Environmental factors trigger entry into lytic cycle 16-6
  7. 7. Figure 16.2 The lytic and lysogenic cycles in prokaryotes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1 ATTACHMENT Capsid combines with receptor. bacterial nucleic acid cell wall bacterial capsid DNA 5 RELEASE 2a PENETRATION 2b INTEGRATION Viral DNA is New viruses leave host cell. Viral DNA enters host. integrated into bacterial DNA and then is passed on when bacteria reproduce. LYTIC viral CYCLE DNA viral DNA LYSOGENIC CYCLE 4 MATURATION 3 BIOSYNTHESIS Viral components are assembled. Viral components are synthesized. capsid prophage viral DNA daughter cells 16-7
  8. 8. 16.3 Plant diseases caused by Viruses Most plant viruses are RNA viruses Generalized symptoms  Stunted growth; discoloration of leaves, flowers, and fruits; death of stems, leaves, and fruits; irregularities in fruit size; etc. Viruses seldom kill their plant hosts Spread by variety of mechanisms 16-8
  9. 9. Figure 16.3A The tobacco mosaic virus (TMV) is responsible fordiscoloration in the leaves of tobacco plants 16-9
  10. 10. Figure 16.3B A virus isresponsible for thevariegation andstreaking in Rembrandttulips Viruses used intentionally to produce streaking Weakens plant and it does not live long 16-10
  11. 11. HOW BIOLOGY IMPACTS OUR LIVES 16A Humans Suffer from Emergent Viral Diseases Emergent diseases – newly recognized as infectious Viruses are constantly in a state of evolutionary flux  Can acquire new spikes to allow entry into new cells Virus that cannot pass from human to human after jumping from an animal host will not be capable of causing an epidemic  A large-scale infection of many persons Some emergent diseases are transmitted by vectors  Mosquitoes used by several viral diseases 16-11
  12. 12. HOW BIOLOGY IMPACTS OUR LIVES 16A Humans Suffer from Emergent Viral Diseases H1N1 virus  Usually found in pigs, in humans it causes the symptoms of flu  Named after spikes H1 and N1 Severe acute respiratory syndrome (SARS)  Causes high fever, body aches, and pneumonia Avian influenza (or bird flu)  Disease does not often spread from chickens to humans, nor is it efficiently transmitted among humans Ebola  1 of a number of viruses that cause hemorrhagic fever  Highly contagious and fatal  Vector and animal reservoir unknown 16-12
  13. 13. 16.4 Viruses reproduce inside animal cells and cause diseases Life cycle of a DNA virus in animals and humans  Attachment: Glycoprotein spikes projecting through the envelope allow the virus to bind to host cells  Penetration: After the viral particle enters the host cell, uncoating follows and viral DNA enters the host  Biosynthesis: The capsid and other proteins are synthesized by host cell ribosomes according to viral DNA instructions  Maturation: Viral proteins and DNA replicates are assembled to form new viral particles  Release: In an enveloped virus, budding occurs and the virus develops its envelope 16-13
  14. 14. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1 Attachment: Spike Figure 16.4 combines with receptor. capsid Replication of an animal virus2 Penetration: Virus enters cell, and uncoating occurs. envelope uncoating spike Cytoplasm nucleic viral DNA acid (DNA) nuclear plasma pore membrane 3a Biosynthesis: Viral proteins are synthesized.Nucleus ribosome viral mRNA capsid protein 3b Biosynthesis: ER Many strands of DNA are produced. 16-14
  15. 15. Figure 16.4Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. capsid Replication of an animal virus (Cont.) viral spikes 4 Maturation: Viral components are assembled. 5 Release: Budding gives virus an envelope. 16-15
  16. 16. 16-16
  17. 17. 16.5 HIV (the AIDS virus) is a retroviruses Genome consists of RNA, instead of DNA Retrovirus  Uses reverse transcription from RNA into DNA in order to insert a complementary copy of its genome into the host’s genome  Uses reverse transcriptase enzyme HIV provirus  Viral DNA integrated into host DNA.  Usually transmitted to another person by means of cells that contain proviruses Emergent viral disease that jumped from chimpanzees to humans 16-17
  18. 18. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 16.5 Reproduction 1 of HIV Attachment receptor envelope spike 2 Penetration capsid nuclear 3 pore Reverse transcription viral RNA reverse transcriptase cDNA 4 Replication Integration host ribosome DNA 5 Biosynthesis viral mRNA provirus viral ER enzyme 16-18
  19. 19. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Replication 4 Integration Figure 16.5 host Reproduction of HIV (Cont.) ribosome DNA 5 Biosynthesis viral mRNA provirus viral ER enzyme capsid protein 6 spike Maturation viral RNA 7 Release 16-19
  20. 20. Prions Prions  Protein infectious particles  Misfolded proteins whose presence causes other proteins to also become misfolded  Cause rare but serious brain diseases, such as Creutzfeldt-Jakob Disease (CJD) 16-20
  21. 21. Figure 16B.1 A virus is less complex than a prokaryote, because all it takes is acapsid surrounding a genetic material. Like this one, some viruses use RNA astheir genetic material Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. protein unit RNA caspid 16-21
  22. 22. Figure 16B.2 A prokaryote is more complex, both metabolically and structurally,than a virus. Like this one, prokaryotes always use DNA as their genetic material Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ribosomes DNA plasma enzymatic membrane proteins cellwall phospholipid bilayer 16-22
  23. 23. Figure 16.6B Chemical evolution at hydrothermal vents Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. plume of hot water rich in iron sulfides hydrothermal vent © Ralph White/Corbis 16-23
  24. 24. 16.9 Prokaryotes have unique structural features Bacteria & Archaea are in separate domains due to molecular and cellular differences Unicellular organisms / Prokaryotic Lack a eukaryotic nucleus and membranous organelles  Nucleoid – dense area with a single chromosome  May have plasmids – accessory rings of DNA Cell wall strengthened by peptidoglycan  May have capsule or slime layer 16-24
  25. 25. 16.9 Prokaryotes have unique structural features Appendages:  Pili – short, for attachment  Flagella – longer, for movement Three Basic Shapes of Prokaryotes  Cocci (sing., coccus) – round or spherical  Bacilli (sing., bacillus) – rod-shaped  Spirilla (sing., spirillum) – spiral- or helical-shaped 16-25
  26. 26. Figure 16.9A Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Anatomy of bacterium flagella piliribosome 1 µmnucleoidplasma membranecell wallcapsule (bacterium, whole): © Ralph A. Slepecky/Visuals Unlimited; (bacterium, circle): Courtesy Harley W. Moon, U.S. Dept. of Agriculture 16-26
  27. 27. Figure 16.9B The three shapes of bacteria 16-27
  28. 28. 16.10 Prokaryotes reproduce by binary fission Reproduce asexually using binary fission  Results in two prokaryotes of equal size  Genetically identical (but higher mutation rate)  Not mitosis  Three steps:  1. DNA replication  2. Chromosome segregation  3. Cytokinesis 16-28
  29. 29. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.1 DNA replication Figure 16.10 Binary fission results in two bacteria2 Chromosome segregation3 Cytokinesis Daughter cells 16-29
  30. 30. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. cytoplasm cell wall nucleoid Cytokinesis 0.5 µm © CNRI/SPL/Photo Researchers, Inc.Figure 16.10 Binary fission results in two bacteria (Cont.) 16-30
  31. 31. Some bacteria form Endospores When faced with unfavorable environmental conditions, some bacteria form endospores  A portion of the cytoplasm and a copy of the chromosome dehydrate and are then encased by a heavy, protective spore coat Spores survive in the harshest of environments and for very long periods of time Not a means of reproduction 16-31
  32. 32. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. endosporeendospore withinClostridium tetani. © Alfred Pasieka/SPL/Photo Researchers, Inc. 16-32
  33. 33. 16.11 Gene are transfer between bacteria1. Transformation  Recipient picks up “free DNA” from its surroundings1. Conjugation  Donor bacterium passes DNA to the recipient by way of a conjugation pilus  Plasmid – small circle of DNA1. Transduction  Bacteriophages carry portions of bacterial DNA from a donor cell to a recipient 16-33
  34. 34. Figure 16.11A Gene transfer by Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. donor cell recipient cell transformationLysis of DNAdonor cellreleasesDNA. Donor DNA is taken up by recipient. 16-34
  35. 35. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. donor cell recipient cell Figure 16.11B Gene transfer by conjugation donor cell plasmid DNA Donor DNA is transferred directly to recipient through a conjugation pilus. 16-35
  36. 36. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. donor cell recipient cell Figure 16.11C Gene transfer by transduction Bacteriophage infects a cell. Donor DNA is picked up by bacteriophage Donor DNA transferred when bacteriophage infects recipient. 16-36
  37. 37. Prokaryotes have various means of nutrition Obligate Anaerobes  Unable to grow in the presence of free oxygen  A few serious illnesses – such as botulism, gas gangrene, and tetanus – are caused by anaerobic bacteria Facultative anaerobes  Able to grow in either presence or absence of oxygen Most prokaryotes are aerobic and require a constant supply of oxygen 16-37
  38. 38.  Autotrophic Prokaryotes  Produce their own organic nutrients / “self-feeding”  Photoautotrophs  Use solar energy to reduce carbon dioxide to organic compounds  Chemosynthetic  Remove electrons from inorganic compounds use them to reduce CO2 to an organic molecule  Ex: Bacteria in a hydrothermal vent 16-38
  39. 39. Figure 16.12A Some anaerobic photosynthetic bacteria live in themuddy bottoms of eutrophic lakes 16-39
  40. 40. Figure 16.12B Some chemosynthetic prokaryotes live at hydrothermalvents Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. tubeworm clam © Science VU/Visuals Unlimited 16-40
  41. 41.  Heterotrophic Prokaryotes (“other feeding”)  Take in organic nutrients  Saprophytic bacteria  Ex: Decomposers in soil  Symbiosis: Two different species living together.  Mutualism – both species benefit  Commensalism– one species benefits, no effect on the other species.  Parasitism – one species benefits, one is harmed. 16-41
  42. 42. 16.13 The cyanobacteria are ecologically important organisms Pigments occur in the membrane of flattened disks called thylakoids Perform photosynthesis like plants Believed to be responsible for introducing oxygen into the atmosphere Some possess heterocysts for nitrogen fixation Common in water, soil, and moist surfaces Some are symbiotic with other organisms (e.g. lichens are cyanobacteria and fungi) 16-42
  43. 43. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. DNA thylakoids cell wall storage granule plasma membrane Oscillatoria cell heterocystGloeocapsa, a unicellular form Anabaena, a colonial form Oscillatoria, a filamentous form (Gloeocapsa): © Runk/Schoenberger/Grant HeilmanPhotography; (Anabaena): © Philip Sze/Visuals Unlimited; (Oscillatoria): © Tom Adams/Visuals Unlimited FIGURE 16.13 Diversity among the cyanobacteria 16-43
  44. 44. 16.14 Archaea live in extreme environments Structure and Function  No peptidoglycan in cell wall  Ex: Methanogens-produce methane from the decomposition of organic matter Archaea are found in extreme environments  Halophiles-organism that requires a salty environment  Thermoacidophiles-environments are extremely acidic with high temperatures 16-44
  45. 45. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Methanosarcina mazei (swamp): © altrendonature/Getty Images; (inset): © Ralph Robinson/Visuals UnlimitedFigure 16.14A Methanogen habitat and structure 16-45
  46. 46. Figure 16.14B Halophile habitat and structure Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Great SaltLake, Utah Halobacterium salinarium (Great Salt Lake): © John Sohlden/Visuals Unlimited; (inset): FromJ.T. Staley, et al., Bergeys Manual of Systematic Bacteriology, Vol. 13, © 1989Williams and Wilkins Col, Baltimore. Prepared by A.L. Usted Photography by Dept. of Biophysics, Norwegian Institute of Technology 16-46
  47. 47. Figure 16.14C Thermoacidophile habitat and structure Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Boiling springs and geysers in Sulfolobus Yellowstone National Park acidocaldarius (geysers): © JeffLepore/Photo Researchers, Inc.; (inset): Courtesy Dennis W. Grogan, University of Cincinnati 16-47
  48. 48. 16.15 Prokaryotes have medical and environmental importance Vast majority of bacterial species are not pathogenic to humans Some bacteria are pathogenic  Tuberculosis (TB) kills more people worldwide than any other infectious disease  Caused by Mycobacterium tuberculosis 16-48
  49. 49. 16-49
  50. 50. Prokaryotes are important in the environment  Ancient photosynthetic cyanobacteria released copious amounts of oxygen  Bacteria break down and recycle nutrients in the soil  Prokaryotes play an essential role in the carbon nitrogen, sulfur, and phosphorus environmental cycles 16-50
  51. 51. HOW BIOLOGY IMPACTS OUR LIVES 16D Disease-causing Microbes Can Be Biological Weapons Biological warfare is the use of viruses and bacteria, or their toxins, as weapons of war Bioterrorists prefer pathogens that are  Highly contagious, consistently produce a desired detrimental effect on a population, have a short incubation period, and are easy to disseminate and deliver to a population In addition to humans, valuable animals and crops can be the targets of biological attacks Vaccines and preventives may be the best way to counter biological agents 16-51
  52. 52. Connecting the Concepts: Chapter 16 Viruses are noncellular, disease-causing agents Prokaryotes are cellular, but their structure is simpler than that of eukaryotes Many prokaryotes can live in extreme environments. Not all bacteria cause diseases, but the few that do infect humans can be deadly. 16-52

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