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Prokaryotes and Viruses

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Presentation on theme: "Prokaryotes and Viruses"— Presentation transcript:

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)







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