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Prokaryotes and Viruses 1. West Nile Virus 2  One of several mosquito-borne viruses in the United States that can infect people  The virus exists in.

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Presentation on theme: "Prokaryotes and Viruses 1. West Nile Virus 2  One of several mosquito-borne viruses in the United States that can infect people  The virus exists in."— Presentation transcript:

1 Prokaryotes and Viruses 1

2 West Nile Virus 2

3  One of several mosquito-borne viruses in the United States that can infect people  The virus exists in nature primarily through a transmission cycle involving mosquitoes and birds.  Mosquitoes become infected with West Nile virus (WNV) when they feed on infected birds 3

4 West Nile Virus Symptoms  Majority of people that become infected with the West Nile virus have no illness or experience only a mild flu-like illness  May include fever, headache and body aches lasting only a few days  Some persons may also have a mild rash or swollen lymph glands  Less than one percent of those infected may develop meningitis or encephalitis, the most severe forms of the disease 4

5  Alexander the Great, 336 B.C., conquered a vast empire  It’s speculated that his demise was due to West Nile encephalitis  There is still no human vaccine for West Nile virus How Long has the West Nile Virus Been Around? 5

6  West Nile Virus is pathogenic, it invades its host and multiplies, causing disease  It’s a flavivirus, traveling inside mosquitoes which act as the transferring agent from host to host West Nile Virus Takes Off 6

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9 Impacts, Issues Video West Nile Virus Takes Off 9

10 Microorganisms  Single-celled organisms that are too small to be seen without a microscope  Bacteria are the smallest living organisms  Viruses are smaller but are not alive 10

11 The Prokaryotes  Only two groups  Archaebacteria and Eubacteria  Arose before the eukaryotes 11

12 Prokaryotic Characteristics  No membrane-bound nucleus  Single chromosome  Cell wall (in most species)  Prokaryotic fission  Metabolic diversity 12

13 Prokaryotic Body Plan bacterial flagellum pilus capsule cell wall plasma membrane cytoplasm DN A ribosomes in cytoplasm 13

14 pilus bacterial flagellum cell wall outer capsule plasma membrane cytoplasm, with ribosomes DNA, in nucleoid Prokaryotic Body Plan 14

15 Prokaryotic body plan Prokaryotic Body Plan 15

16 Bacterial Shapes coccusbacillus spirillum 16

17 Bacterial Shapes 17

18 Bacterial Shapes 18

19 Bacterial Shapes 19

20 sex pilus Bacterial Shapes 20

21 Metabolic Diversity  Photoautotrophs  Chemoautotrophs  Chemoheterotrophs 21

22 Gram Stain 22

23 Gram stain Gram Stain 23

24 Bacterial Genes  Bacteria have a single chromosome Circular molecule of DNA Circular molecule of DNA  Many bacteria also have plasmids Self-replicating circle of DNA that has a few genes Self-replicating circle of DNA that has a few genes Can be passed from one cell to another Can be passed from one cell to another 24

25 Prokaryotic Fission 25


27 Prokaryotic Fission 27

28 Prokaryotic Fission 28

29 Prokaryotic Fission 29

30 Prokaryotic Fission 30

31 Prokaryotic Fission 31

32 Prokaryotic Fission 32

33 Prokaryotic Fission 33

34 parent DNA molecule DNA copy DNA replication completed DNA replication begins Bacterium before DNA replication bacterial chromosome 34

35 Membrane growth moves DNA molecules apart New membrane and cell-wall material deposited Cytoplasm divided in two 35

36 Prokaryotic fission Prokaryotic Fission - 3 36

37 Conjugation Transfer of plasmid 37

38 nicked plasmidconjugation tube

39 Prokaryotic conjugation Conjugation 39

40 Prokaryotic Classification EUBACTERIA (Bacteria) ARCHAEBACTERIA (Archaea) EUKARYOTES (Eukarya) Traditionally classified by numerical taxonomy Now increased use of comparative biochemistry 40

41 DOMAIN BACTERIA to ancestors of eukaryotic cells biochemical and molecular origin of life Prokaryotic Classification 41

42 Eubacteria  Includes most familiar bacteria  Have fatty acids in plasma membrane  Most have cell wall; always includes peptidoglycan  Classification based largely on metabolism 42

43 Eubacterial Diversity  Photoautotrophic Aerobic (Cyanobacteria) Aerobic (Cyanobacteria) Anaerobic (Green bacteria) Anaerobic (Green bacteria)  Chemoautotrophic Important in nitrogen cycle Important in nitrogen cycle  Chemoheterotrophic Largest group Largest group 43

44 Examples of eubacteria Eubacteria 44

45 Eubacterial Diversity 45

46 Eubacterial Diversity 46

47 Eubacterial Diversity 47

48 Some Pathogenic Eubacteria  Most are chemoheterotrophs E. coli strains E. coli strains Clostridium botulinum Clostridium botulinum Clostridium tetanus Clostridium tetanus Borrelia burgdorferi Borrelia burgdorferi Rickettsia rickettsii Rickettsia rickettsii 48

49 resting spore heterocyst photo- synthetic cell Some Pathogenic Eubacteria 49

50 Some Pathogenic Eubacteria 50

51 Some Pathogenic Eubacteria 51

52 DNA spore coat capsule around cell wall Some Pathogenic Eubacteria 52

53 Bacterial Behavior  Bacteria move toward nutrient-rich regions  Aerobes move toward oxygen; anaerobes avoid it  Photosynthetic types move toward light  Magnetotactic bacteria swim downward  Myobacteria show collective behavior 53

54 Bacterial Behavior 54

55 Archaebacteria 55

56 Archaebacteria Methanogens Extreme halophiles Extreme thermophiles 56

57 Methanogens 57

58 Methanogens 58

59 Extreme Halophiles 59

60 Extreme Thermophiles 60

61 Extreme Thermophiles 61

62 Virus  Noncellular infectious agent  Protein wrapped around a nucleic acid core  Cannot reproduce itself; can only be reproduced using a host cell 62

63 Viral Body Plans  Genetic material is DNA or RNA  Coat is protein Complex virus (bacteriophage) Polyhedral virusHelical virus 63

64 Enveloped Virus (HIV) lipid envelope (derived from host) viral RNA reverse transcriptase viral coat (proteins) viral protein 64

65 viral RNA protein subunits of coat 18 nm diameter, 250 nm length Enveloped Virus (HIV) 65

66 80 nm diameter Enveloped Virus (HIV) 66

67 DNA protein coat sheath base plate tail fiber 65–nm diameter head, 225 nm total length Enveloped Virus (HIV) 67

68 Enveloped Virus (HIV) lipid envelope: proteins span the envelope, line its inner surface, spike out above it viral RNA reverse transcriptase viral coat (proteins) 100-120 nm diameter 68

69 Body plans of viruses Viral Body Plans 69

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72 Viruses 72

73 Viruses 73

74 Viruses 74

75 Viruses 75

76 Viral Multiplication - Basic Steps  Attach to host cell  Enter host (virus or just genetic material)  Direct host to make viral genetic material and protein  Assemble viral nucleic acids and proteins  Release new viral particles 76

77 Bacteriophage multiplication cycles Viral Replication 77

78 a Virus particle injects genetic material into a suitable host cell after binding to its wall. e Lysis of host cell is induced; infectious particles escape. d The coats get tail fibers, other parts. c Viral proteins are assembled into coats around viral DNA. b Viral DNA directs host cell to make viral proteins and replicate viral DNA. Lytic Pathway a-1 Viral DNA is integrated into the host’s chromosome. a-4 Viral DNA is excised from the chromosome. a-2 Before prokaryotic fission, the bacterial chromosome with the integrated viral DNA is replicated. a-3 After cell division, each daughter cell will have recombinant DNA. Lysogenic Pathway Fig. 21-15, p.344 Lytic Pathway 78

79 Lytic Pathway 79

80 Lytic Pathway Virus particles bind to wall of suitable host. Viral genetic material enters cell cytoplasm. Viral DNA directs host machinery to produce viral proteins and viral DNA. Viral protein molecules are assembled into coats; DNA is packaged inside. Tail fibers and other parts are added to coats. Lysis of host cell is induced; infectious particles escape. 80

81 Lytic pathway Lytic Pathway 81

82 Lysogenic Pathway Viral DNA usually becomes integrated into the bacterial chromosome. Prior to prokaryotic fission, the chromosome and integrated viral DNA are replicated. After binary fission, each daughter cell will have recombinant DNA. Viral DNA is excised from chromosome and cell enters lytic pathway. 82

83 Lysogenic pathway Lysogenic Pathway 83

84 Replication of an Enveloped Virus viral DNA some proteins for viral coat Replication of viral DNA DNA virus particle plasma membrane of host cell nuclear envelope other proteins for viral envelope Translation Transcription of viral DNA 84

85 Replication of an Enveloped Virus 85

86 Enveloped DNA virus replication Replication of an Enveloped Virus 86

87 Nature of Disease  Contagious disease pathogens must directly contact a new host  Epidemic  Pandemic (AIDS)  Sporadic  Endemic 87

88 Evolution and Disease  Host and pathogen are coevolving  If a pathogen kills too quickly, it might disappear along with the individual host  Most dangerous if pathogen Is overwhelming in numbers Is overwhelming in numbers Is in a novel host Is in a novel host Is a mutant strain Is a mutant strain 88

89 Mycobacterium tuberculosis 89

90 SARS virus 90

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92 New Threats  Emerging Pathogens Ebola virus Ebola virus Monkeypox virus Monkeypox virus SARS virus SARS virus  Drug-resistant strains  Food poisoning E. coli E. coli Salmonella Salmonella 92

93 Viroids  Smaller than viruses  Strands or circles of RNA  No protein-coding genes  No protein coat  Cause many plant diseases 93

94 Prions  Small proteins  Linked to human diseases Kuru Kuru Creutzfeldt-Jakob disease (CJD) Creutzfeldt-Jakob disease (CJD)  Animal diseases Scrapie in sheep Scrapie in sheep Bovine spongiform encephalopathy (mad cow disease) Bovine spongiform encephalopathy (mad cow disease) 94

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