1. Prokaryotes and Viruses

2. West Nile Virus

3. West Nile Virus
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

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

5. How Long has the West Nile Virus Been Around?
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

6. West Nile Virus Takes Off
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

7. West Nile Virus Takes Off

8. West Nile Virus Takes Off

9. West Nile Virus Takes Off
Impacts, Issues Video
West Nile Virus Takes Off

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

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

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

13. Prokaryotic Body Plan DNA capsule plasma membrane
ribosomes in cytoplasm
bacterial flagellum
pilus
cell wall
cytoplasm

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

15. Prokaryotic Body Plan
Prokaryotic body plan

16. Bacterial Shapes
coccus
bacillus
spirillum

17. Bacterial Shapes

18. Bacterial Shapes

19. Bacterial Shapes

20. Bacterial Shapes
sex pilus

21. Metabolic Diversity
Photoautotrophs
Chemoautotrophs
Chemoheterotrophs

22. Gram Stain

23. Gram Stain
Gram stain

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

25. Prokaryotic Fission

27. Prokaryotic Fission

28. Prokaryotic Fission

29. Prokaryotic Fission

30. Prokaryotic Fission

31. Prokaryotic Fission

32. Prokaryotic Fission

33. Prokaryotic Fission

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

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

36. Prokaryotic Fission - 3
Prokaryotic fission

37. Conjugation
Transfer of plasmid

38. nicked plasmid
conjugation tube

39. Prokaryotic conjugation

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

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

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

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

44. Examples of eubacteria

45. Eubacterial Diversity

46. Eubacterial Diversity

47. Eubacterial Diversity

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

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

50. Some Pathogenic Eubacteria

51. Some Pathogenic Eubacteria

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

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

54. Bacterial Behavior

55. Archaebacteria

56. Archaebacteria
Methanogens
Extreme halophiles
Extreme thermophiles

57. Methanogens

58. Methanogens

59. Extreme Halophiles

60. Extreme Thermophiles

61. Extreme Thermophiles

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

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

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

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

66. Enveloped Virus (HIV)
80 nm diameter

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

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

69. Viral Body Plans
Body plans of viruses

72. Viruses

73. Viruses

74. Viruses

75. Viruses

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

77. Bacteriophage multiplication cycles
Viral Replication
Bacteriophage multiplication cycles

78. e Lysis of host cell is induced; infectious particles escape.
Lytic Pathway
d The coats get tail fibers, other parts.
Lytic
Pathway
a Virus particle injects genetic material into a suitable host cell after binding to its wall.
c Viral proteins are assembled into coats around viral DNA.
b Viral DNA directs host cell to make viral proteins and replicate viral DNA.
a-1 Viral DNA is integrated into the host’s chromosome.
a-4 Viral DNA is excised from the chromosome.
Lysogenic
Pathway
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.
Fig , p.344

79. Lytic Pathway

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

81. Lytic Pathway
Lytic pathway

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

83. Lysogenic Pathway
Lysogenic pathway

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

85. Replication of an Enveloped Virus

86. Replication of an Enveloped Virus
Enveloped DNA virus replication

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

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 in a novel host
Is a mutant strain

89. Mycobacterium tuberculosis

90. SARS virus

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

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

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