Prokaryotes and
Viruses
1
West Nile Virus
2
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
3
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
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
5
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
6
West Nile Virus Takes Off
7
West Nile Virus Takes Off
8
Impacts, Issues Video
West Nile Virus Takes
Off
9
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
The Prokaryotes
 Only
two groups
 Archaebacteria
and
Eubacteria
 Arose
before the eukaryotes
11
Prokaryotic Characteristics
 No
membrane-bound nucleus
 Single
 Cell
chromosome
wall (in most species)
 Prokaryotic
 Metabolic
fission
diversity
12
Prokaryotic Body Plan
DN
A
capsule
bacterial flagellum
pilus
plasma
membrane
cell wall
ribosomes in
cytoplasm
cytoplasm
13
Prokaryotic Body Plan
cytoplasm,
with
ribosomes
DNA, in nucleoid
pilus
bacterial
flagellum
outer capsule
cell wall
plasma
membrane
14
Prokaryotic Body Plan
Prokaryotic body plan
15
Bacterial Shapes
coccus
bacillus
spirillum
16
Bacterial Shapes
17
Bacterial
Shapes
18
Bacterial Shapes
19
Bacterial
Shapes
sex pilus
20
Metabolic Diversity
 Photoautotrophs
 Chemoautotrophs
 Chemoheterotrophs
21
Gram Stain
22
Gram Stain
Gram stain
23
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
24
Prokaryotic Fission
25
Prokaryotic Fission
27
Prokaryotic Fission
28
Prokaryotic Fission
29
Prokaryotic Fission
30
Prokaryotic Fission
31
Prokaryotic Fission
32
Prokaryotic Fission
33
bacterial
chromosome
Bacterium
before
DNA replication
DNA replication
begins
parent
DNA
molecule
DNA replication
completed
DNA copy
34
Membrane growth
moves DNA
molecules apart
New membrane and
cell-wall material
deposited
Cytoplasm
divided in two
35
Prokaryotic Fission - 3
Prokaryotic fission
36
Conjugation
Transfer of plasmid
37
nicked plasmid
conjugation tube
Conjugation
Prokaryotic conjugation
39
Prokaryotic Classification
EUBACTERIA
(Bacteria)
ARCHAEBACTERIA
(Archaea)
EUKARYOTES
(Eukarya)
•Traditionally classified by numerical taxonomy
•Now increased use of comparative biochemistry
40
Prokaryotic Classification
to ancestors of eukaryotic cells
DOMAIN BACTERIA
DOMAIN BACTERIA
biochemical and molecular origin of life
41
Eubacteria

Includes most familiar bacteria

Have fatty acids in plasma membrane

Most have cell wall; always includes
peptidoglycan

Classification based largely on metabolism
42
Eubacterial Diversity
 Photoautotrophic


Aerobic (Cyanobacteria)
Anaerobic (Green bacteria)
 Chemoautotrophic

Important in nitrogen cycle
 Chemoheterotrophic

Largest group
43
Eubacteria
Examples of eubacteria
44
Eubacterial Diversity
45
Eubacterial Diversity
46
Eubacterial Diversity
47
Some Pathogenic Eubacteria
 Most





are chemoheterotrophs
E. coli strains
Clostridium botulinum
Clostridium tetanus
Borrelia burgdorferi
Rickettsia rickettsii
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resting
spore
Some
Pathogenic
Eubacteria
photosynthetic
cell
heterocyst
49
Some
Pathogenic
Eubacteria
50
Some
Pathogenic
Eubacteria
51
Some
Pathogenic
Eubacteria
DNA
spore
coat
capsule
around cell
wall
52
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
Bacterial Behavior
54
Archaebacteria
55
Archaebacteria
Methanogens
Extreme halophiles
Extreme thermophiles
56
Methanogens
57
Methanogens
58
Extreme Halophiles
59
Extreme Thermophiles
60
Extreme Thermophiles
61
Virus
 Noncellular
 Protein
core
infectious agent
wrapped around a nucleic acid
 Cannot
reproduce itself; can only be
reproduced using a host cell
62
Viral Body Plans
Complex virus
(bacteriophage)
 Genetic
material is
DNA or RNA
 Coat is protein
Helical virus
Polyhedral virus
63
Enveloped Virus (HIV)
viral protein
lipid envelope
(derived from
host)
viral RNA
viral coat (proteins)
reverse
transcriptase
64
viral RNA
Enveloped
Virus (HIV)
protein
subunits
of coat
18 nm
diameter
, 250 nm
length
65
Enveloped Virus (HIV)
80 nm diameter
66
Enveloped Virus
(HIV)
65–nm diameter head,
225 nm total length
DNA
protein coat
sheath
base
plate
tail
fiber
67
viral coat
(proteins)
Enveloped Virus (HIV)
reverse
transcriptase
100-120 nm
diameter
viral RNA
lipid envelope: proteins span
the envelope, line its inner
surface, spike out above it
68
Viral Body Plans
Body plans of viruses
69
70
71
Viruses
72
Viruses
73
Viruses
74
Viruses
75
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
 Release
viral nucleic acids and proteins
new viral particles
76
Viral Replication
Bacteriophage multiplication cycles
77
Lytic
Pathway
e Lysis of host cell is induced;
infectious particles escape.
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-2 Before prokaryotic fission,
the bacterial chromosome with
the integrated viral DNA is
replicated.
a-4 Viral DNA is excised
from the chromosome.
Lysogenic
Pathway
a-3 After cell division, each
daughter cell will have recombinant
DNA.
78
Fig. 21-15, p.344
Lytic Pathway
79
Lytic
Pathway
Lysis of host cell is
induced; infectious particles
escape.
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.
80
Lytic Pathway
Lytic pathway
81
Lysogenic
Pathway
Viral DNA usually becomes
integrated into the
bacterial chromosome.
Prior to prokaryotic fission,
the chromosome and
integrated viral DNA are
replicated.
Viral DNA is excised from
chromosome and cell
enters lytic pathway.
After binary fission,
each daughter cell will
have recombinant DNA.
82
Lysogenic Pathway
Lysogenic pathway
83
Replication
of an
Enveloped
Virus
DNA virus particle
plasma
membrane
of host cell
Replication
of viral
DNA
Transcription
of viral DNA
viral DNA
Translation
some
proteins for
viral coat
nuclear
envelope
other
proteins
for viral
envelope
84
Replication
of an
Enveloped
Virus
85
Replication of an Enveloped Virus
Enveloped DNA virus replication
86
Nature of Disease
 Contagious
disease pathogens must
directly contact a new host
 Epidemic
 Pandemic (AIDS)
 Sporadic
 Endemic
87
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
88
Mycobacterium
tuberculosis
89
SARS virus
90
91
New Threats
 Emerging



Pathogens
Ebola virus
Monkeypox virus
SARS virus
 Drug-resistant
 Food


strains
poisoning
E. coli
Salmonella
92
Viroids
 Smaller
than viruses
 Strands
or circles of RNA
 No
protein-coding genes
 No
protein coat
 Cause
many plant diseases
93
Prions
 Small
proteins
 Linked to human diseases


Kuru
Creutzfeldt-Jakob disease (CJD)
 Animal


diseases
Scrapie in sheep
Bovine spongiform encephalopathy
(mad cow disease)
94
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