1. Biology Sylvia S. Mader Michael Windelspecht
Chapter 20
Viruses, Bacteria and Archaea
Lecture Outline
See separate FlexArt PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes. 1
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1

2. 20.1 Viruses, Viroids, and Prions
Biology, 9th ed,Sylvia Mader
Chapter 21
20.1 Viruses, Viroids, and Prions
Viruses, Bacteria & Archaea
Virus
Associated with a number of plant, animal, and human diseases
Can only reproduce using the metabolic machinery of the host cell
noncellular
May have a DNA or RNA genome.
Invention of the electron microscope allowed these infectious agents to be seen for the first time

3. Viral Diseases in Humans
Biology, 9th ed,Sylvia Mader
Viral Diseases in Humans
Chapter 21
Viruses, Bacteria & Archaea

4. Viruses, Viroids, and Prions
Biology, 9th ed,Sylvia Mader
Chapter 21
Viruses, Viroids, and Prions
Viruses, Bacteria & Archaea
Viral Structure:
nm in diameter
Each type has at least two parts
Capsid: Outer layer composed of protein subunits
Some are enveloped by membrane
Others “naked”
Nucleic acid core: DNA or RNA
Vary in shape

5. Viruses, Viroids, and Prions
Biology, 9th ed,Sylvia Mader
Chapter 21
Viruses, Viroids, and Prions
Viruses, Bacteria & Archaea
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Capsid (protein)
Covering
Envelope (not found in all viruses)
Virus particle
Nucleic acid molecule (DNA or RNA)
Inner core
Various proteins (enzymes)

6. Biology, 9th ed,Sylvia Mader
Viruses
Chapter 21
Viruses, Bacteria & Archaea
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
TEM 80,000X
TEM 90,000X
Adenovirus: DNA virus with a polyhedral capsid and a fiber
at each corner.
T-even bacteriophage: DNA virus with a polyhedral head and
a helical tail.
fiber protein
capsid
fiber
DNA
protein unit
neck
capsid
DNA
tail sheath
tail fiber
pins
base plate a. b.
a: © Dr. Hans Gelderblom/Visuals Unlimited; b: © Eye of Science/Photo Researchers, Inc.

7. Biology, 9th ed,Sylvia Mader
Viruses
Chapter 21
Viruses, Bacteria & Archaea
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
TEM 500,000X
20nm
Tobacco mosaic virus: RNA virus with a helical capsid.
Influenza virus: RNA virus with a spherical capsid surrounded
by an envelope with spikes.
spikes
capsid
RNA
RNA
envelope
capsid c. d. 7
c: © Dr. O. Bradfute/Peter Arnold/Photolibrary; d: © K.G. Murti/Visuals Unlimited

8. Viruses, Viroids, and Prions
Biology, 9th ed,Sylvia Mader
Chapter 21
Viruses, Viroids, and Prions
Viruses, Bacteria & Archaea
Viruses:
Are obligate intracellular parasites
Cannot reproduce outside a living cell
Can be cultured only inside living cells
Chicken egg
Tissue culture

9. Biology, 9th ed,Sylvia Mader
Chapter 21
Culturing Viruses
Viruses, Bacteria & Archaea
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© Ed Degginger/Color Pic Inc.

10. Viruses, Viroids, and Prions
Biology, 9th ed,Sylvia Mader
Chapter 21
Viruses, Viroids, and Prions
Viruses, Bacteria & Archaea
Replication of Viruses:
Gain entry into specific host cell
Capsid (or spikes of the envelope) adhere to specific receptor sites on the host cell surface.
Viral nucleic acid then enters a cell
Viral genome codes for production of protein units in the capsid.
Relies on host cell enzymes, ribosomes, transfer RNA (tRNA), and ATP for its own replication

11. Viruses, Viroids, and Prions
Biology, 9th ed,Sylvia Mader
Chapter 21
Viruses, Viroids, and Prions
Viruses, Bacteria & Archaea
Bacteriophages – Viruses that infect bacterial cells
There are two types of bacteriophage life cycles
The lytic cycle
Viral reproduction occurs
The host cell undergoes lysis
The lysogenic cycle
Viral reproduction does not occur immediately but may occur in the future

12. Viruses, Viroids, and Prions
Biology, 9th ed,Sylvia Mader
Chapter 21
Viruses, Viroids, and Prions
Viruses, Bacteria & Archaea
Lytic cycle may be divided into five stages:
Attachment
Penetration
Biosynthesis
Maturation
Release

13. Viruses, Viroids, and Prions
Biology, 9th ed,Sylvia Mader
Chapter 21
Viruses, Viroids, and Prions
Viruses, Bacteria & Archaea
In the lysogenic cycle, the phage becomes a prophage
Becomes integrated into the host genome
Becomes latent
May later reenter the lytic cycle

14. Lytic and Lysogenic Cycles in Prokaryotes
Biology, 9th ed,Sylvia Mader
Chapter 21
Viruses, Bacteria & Archaea
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1. ATTACHMENT
Capsid combines with receptor.
nucleic acid
bacterial
cell wall
bacterial
DNA
capsid

15. Lytic and Lysogenic Cycles in Prokaryotes
Biology, 9th ed,Sylvia Mader
Lytic and Lysogenic Cycles in Prokaryotes
Chapter 21
Slide #15
Viruses, Bacteria & Archaea
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1. ATTACHMENT
Capsid combines with receptor.
bacterial
cell wall
nucleic acid
bacterial
DNA
capsid
5. RELEASE
New viruses leave host cell.
2. PENETRATION
Viral DNA enters host.
INTEGRATION Viral DNA is integrated
into bacterial DNA and then is passed
on when bacteria reproduce.
LYTIC
CYCLE
viral
DNA
viral
DNA
LYSOGENIC
CYCLE
4. MATURATION
Assembly of viral components.
3. BIOSYNTHESIS
Viral components are synthesized.
prophage 15
daughter cells

16. Lytic and Lysogenic Cycles in Prokaryotes
Biology, 9th ed,Sylvia Mader
Chapter 21
Slide #16
Viruses, Bacteria & Archaea
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 16
© Eye of Science/Photo Research, Inc.

17. Lytic and Lysogenic Cycles in Prokaryotes
Biology, 9th ed,Sylvia Mader
Lytic and Lysogenic Cycles in Prokaryotes
Chapter 21
Slide #17
Viruses, Bacteria & Archaea
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1. ATTACHMENT
Capsid combines with receptor.
bacterial
cell wall
nucleic acid
bacterial
DNA
capsid
5. RELEASE
New viruses leave host cell.
2. PENETRATION
Viral DNA enters host.
INTEGRATION Viral DNA is integrated
into bacterial DNA and then is passed
on when bacteria reproduce.
LYTIC
CYCLE
viral
DNA
viral
DNA
LYSOGENIC
CYCLE
4. MATURATION
Assembly of viral components.
3. BIOSYNTHESIS
Viral components are synthesized.
prophage 17
daughter cells
© Eye of Science/Photo Research, Inc.

18. Viruses, Viroids, and Prions
Biology, 9th ed,Sylvia Mader
Chapter 21
Viruses, Viroids, and Prions
Viruses, Bacteria & Archaea
Reproduction of Animal Viruses:
Animal virus enters the host cell
Uncoating releases viral DNA or RNA
Budding:
Viral particles released in a bud
Acquires a membranous envelope
Retroviruses (AIDS)
Contain reverse transcriptase
Carries out RNA  cDNA reverse transcription
cDNA becomes integrated into host DNA
Replicated as host DNA replicates
Viral DNA is transcribed; new viruses are produced

19. Reproduction of the Retrovirus HIV
Biology, 9th ed,Sylvia Mader
Chapter 21
Slide #19
Viruses, Bacteria & Archaea
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1. Attachment
receptor
envelope
spike
2. Entry
capsid
nuclear
pore
3. Reverse transcription
viral RNA
reverse transcriptase
cDNA
Integration
host DNA
ribosome
4. Biosynthesis
viral
mRNA
provirus ER
viral
enzyme
capsid
protein
5. Maturation
viral RNA 19
6. Release

20. Biology, 9th ed,Sylvia Mader
Chapter 21
Flu Pandemic
Viruses, Bacteria & Archaea
A flu virus has an H (hemagglutinin) spike and an N (neuraminidase) spike
H spike allows the virus to bind to the receptor
16 different types
N spike attacks host plasma membranes
Allows mature viruses to exit the cell
9 different types
Each type of spike can occur in different varieties
Our immune system only recognizes H spikes and N spikes it has been exposed to

21. Spikes of Bird Flu Virus
Biology, 9th ed,Sylvia Mader
Chapter 21
Spikes of Bird Flu Virus
Viruses, Bacteria & Archaea
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
capsid
mutation 1
mutation 2
RNA genome
envelope
N (neuraminidase)
spike
H (hemagglutinin)
spike
a. Viral genetic mutations occur in a bird host
Bird
Flu
virus
Human
flu virus
combination
In host cell
b. Combination of viral genes occurs in human host

22. Viruses, Viroids, and Prions
Biology, 9th ed,Sylvia Mader
Chapter 21
Viruses, Viroids, and Prions
Viruses, Bacteria & Archaea
Viruses are best known for causing infectious diseases in plants and animals
Herpes, HIV, cancer
Viruses lack metabolism; thus, antibiotics have no effect
Viroids
Naked strands of RNA
Many crop diseases
Prions
Protein molecules with contagious tertiary structure
Some human and other animal diseases - Mad cow disease

23. Biology, 9th ed,Sylvia Mader
Chapter 21
20.2 The Prokaryotes
Viruses, Bacteria & Archaea
Include bacteria and archaea, which are fully functioning cells
Microscopic
Range in size from 1-10 µm in length and µm in width
Abundant in air, water, and soil and on most objects
Louis Pasteur showed that a previously sterilized broth cannot become cloudy with growth unless it is exposed directly to the air

24. Biology, 9th ed,Sylvia Mader
Chapter 21
Pasteur’s Experiment
Viruses, Bacteria & Archaea
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
HYPOTHESIS A: Bacteria arise spontaneously in a broth.
HYPOTHESIS B: Bacteria in the air contaminate a broth.
FIRST EXPERIMENT
SECOND EXPERIMENT
flask is open to air
flasks outside building
opened briefly
boiling to
sterilize
broth
boiling to
sterilize
broth
89% show growth
air here is pure
air enters here
flasks inside building
opened briefly
boiling to
sterilize
broth
bacteria collect here
32% show growth
100% have no growth
CONCLUSION:
Hypothesis B is supported because relative concentrations of bacteria in
the air explain the results.
CONCLUSION:
Hypothesis B is supported because when air reaching the broth contains
no bacteria, the flask remains free of growth.

25. Biology, 9th ed,Sylvia Mader
Chapter 21
The Prokaryotes
Viruses, Bacteria & Archaea
Prokaryote Structure
Lack a membrane-bounded nucleus (DNA in nucleoid region)
Outer cell wall
Some move by means of flagella
Lack membranous organelles
May have accessory rings of DNA (plasmids)

26. Biology, 9th ed,Sylvia Mader
Chapter 21
Prokaryote Structure
Viruses, Bacteria & Archaea
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Glycocalyx
Cell envelope
Cell wall
Plasma membrane
Nucleoid
Prokaryotic cell
Cytoplasm
Ribosomes
Thylakoids (cyanobacteria)
Flagella
Appendages
Conjugation pilus
Fimbriae

27. Features of Prokaryotic Cells
Biology, 9th ed,Sylvia Mader
Features of Prokaryotic Cells
Chapter 21
Viruses, Bacteria & Archaea
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
capsule
gel-like coating outside the cell wall
made up of a polysaccharide layer
called glycocalyx. a. b.
plasma membrane
sheet that surrounds the
cytoplasm and regulates
entrance and exit of molecules
plasma
membrane
cell wall
structure that provides
support and shapes the cell
cell wall
fimbriae
hairlike bristles that allow
adhesion to surfaces
capsule
hook
nucleoid
location of the
bacterial chromosome
ribosome
site of protein
synthesis
filament
conjugation pilus
elongated, hollow appendage
used to transfer DNA to other cells
basal body
cytoplasm
semifluid solution surrounded by the plasma
membrane; contains nucleoid and ribosomes
flagellum
rotating filament that propels the cell

28. Biology, 9th ed,Sylvia Mader
Chapter 21
The Prokaryotes
Viruses, Bacteria & Archaea
Reproduction in Prokaryotes
Asexual
Prokaryotes reproduce asexually by means of binary fission
Mutations are generated rapidly and passed on to offspring quickly
Prokaryotes are haploid
Mutations are immediately subjected to natural selection
Some bacteria form resistant endospores under unfavorable conditions

29. Biology, 9th ed,Sylvia Mader
Chapter 21
Binary Fission
Viruses, Bacteria & Archaea
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
cytoplasm
cell wall
nucleoid
0.5 µm
© CNRI/SPL/Photo Researchers, Inc.

30. Biology, 9th ed,Sylvia Mader
Chapter 21
The Prokaryotes
Viruses, Bacteria & Archaea
Methods of genetic recombination in the prokaryotes:
Conjugation
Conjugation pilus forms between two cells
Donor cell passes DNA to recipient cell through the pilus
Transformation
Occurs when bacterium picks up free pieces of DNA from other prokaryotes
Becomes incorporated into genome
Transduction
Occurs when bacteriophages carry portions of bacterial DNA from one cell to another
Serve as vectors

31. Biology, 9th ed,Sylvia Mader
Chapter 21
20.3 The Bacteria
Viruses, Bacteria & Archaea
Bacteria are the more common type of
prokaryote.
Over 9,000 different bacteria have been named.
Most bacterial cells are protected by a cell wall
Contains peptidoglycan
Bacteria are commonly differentiated using the Gram stain procedure
When washed after staining:
Gram-positive bacteria retain dye and appear purple
Gram-negative bacteria do not retain dye and appear pink
The difference is dependent on the construction of the cell wall

32. Biology, 9th ed,Sylvia Mader
Chapter 21
The Bacteria
Viruses, Bacteria & Archaea
Structure of cell wall also of diagnostic use
Bacteria can be further classified in terms of their three basic shapes
Spiral (spirilli),
Rod (bacilli), and
Round (cocci)

33. Biology, 9th ed,Sylvia Mader
Chapter 21
Diversity of Bacteria
Viruses, Bacteria & Archaea
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a. Spirillum:
Spirillum volutans
SEM 3,520X
b. Bacilli:
Bacillus anthracis
SEM 35,000X
c. Cocci:
Streptococcus thermophilus
SEM 6,250X
a: © Dr. Richard Kessel & Dr. Gene Shih/Visuals Unlimited; b: © Gary Gaugler/Visuals Unlimited; c: © SciMAT/Photo Researchers, Inc.

34. Biology, 9th ed,Sylvia Mader
Chapter 21
The Bacteria
Viruses, Bacteria & Archaea
Bacterial Metabolism:
Oxygen requirements:
Obligate aerobes – unable to grow in the absence of free oxygen
Obligate anaerobes – unable to grow in the presence of free oxygen
Facultative anaerobes – able to grow in either the presence or absence of free oxygen

35. Biology, 9th ed,Sylvia Mader
Chapter 21
The Bacteria
Viruses, Bacteria & Archaea
Autotrophic Bacteria:
Photoautotrophs
Use solar energy to reduce carbon dioxide to organic compounds
Photosynthetic
Chemoautotrophs
Oxidize inorganic compounds to obtain energy
Energy is used to reduce CO2 to an organic compound
Chemosynthetic

36. Biology, 9th ed,Sylvia Mader
Chapter 21
The Bacteria
Viruses, Bacteria & Archaea
Heterotrophic Bacteria
Most prokaryotes are chemoheterotrophs that take in organic nutrients
Aerobic saprotrophs decompose most large organic molecules to smaller molecules
Essential components of a healthy ecosystem
May be free-living or symbiotic
Commensalism
One species benefits while the other is left unaffected
Mutualism
Both species benefit from association
Parasitism
Parasite benefits at host expense
Many form endospores

37. Biology, 9th ed,Sylvia Mader
Chapter 21
Nodules of a Legume
Viruses, Bacteria & Archaea
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
root
nodule
Courtesy Nitragin Company, Inc.

38. The Endospore of Clostridium tetani
Biology, 9th ed,Sylvia Mader
Chapter 21
The Endospore of Clostridium tetani
Viruses, Bacteria & Archaea
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
endospore
© Alfred Pasieka/SPL/Photo Researchers, Inc.

39. Bacterial Diseases in Humans
Biology, 9th ed,Sylvia Mader
Bacterial Diseases in Humans
Chapter 21
Viruses, Bacteria & Archaea

40. Viruses, Bacteria & Archaea
Biology, 9th ed,Sylvia Mader
Chapter 21
Slide #40
The Bacteria
Viruses, Bacteria & Archaea
Antibiotic compounds fall into two classes
Compounds that inhibit protein biosynthesis
Erythromycin
Tetracycline
Compounds that inhibit cell wall biosynthesis
Penicillin
Ampicillin
Fluroquinolone
Bacterial resistance to antibiotics is increasing
Genes conferring resistance can be transferred among bacteria by transformation, conjugation, or transduction 40

41. Biology, 9th ed,Sylvia Mader
Chapter 21
The Bacteria
Viruses, Bacteria & Archaea
Cyanobacteria
Formerly called the Blue-Green algae (Cyanophyta)
Cyanobacteria are Gram-negative bacteria that are photosynthetic
Believed to be responsible for introducing oxygen into the primitive atmosphere
Lack visible means of locomotion
Can live in extreme environments
When commensals with fungi, form lichens

42. Diversity Among the Cyanobacteria
Biology, 9th ed,Sylvia Mader
Chapter 21
Diversity Among the Cyanobacteria
Viruses, Bacteria & Archaea
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
DNA
thylakoids
plasma
membrane
cell wall
storagegranule
a. Gloeocapsa
LM 250X
b. Oscillatoria
LM 100X
c. Oscillatoria cell
a: © Michael Abbey/Photo Researchers, Inc.; b: © Tom Adams/Visuals Unlimited

43. Biology, 9th ed,Sylvia Mader
Chapter 21
20.4 The Archaea
Viruses, Bacteria & Archaea
Archaea were earlier considered Bacteria
Carl Woese and George Fox discovered that the base sequence of their rRNA differs from bacteria
Other differences:
Archaea do not have peptidoglycan in their cell walls like the Bacteria
Archaea are biochemically more like Eukarya than Bacteria
Archaea are now thought to be more closely related to Eukarya than to Bacteria

44. Biology, 9th ed,Sylvia Mader
Chapter 21
The Archaea
Viruses, Bacteria & Archaea
Many live in harsh conditions:
Anaerobic marshes
Methanogens
Produce methane from hydrogen gas and carbon dioxide
Salty lakes
Halophiles
Require high salt concentrations for growth
Hot sulfur springs
Thermoacidophiles
Reduce sulfides and survive best at temperatures above 80ºC
Plasma membranes contain unusual lipids that confer tolerance of high temperatures

45. Extreme Habitats: Salt Lakes
Biology, 9th ed,Sylvia Mader
Chapter 21
Viruses, Bacteria & Archaea
Extreme Habitats: Salt Lakes
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a(Main): © John Sohlden/Visuals Unlimited; a (Inset): From J.T. Staley, et al., Bergey's Manual of Systematic Bacteriology, Vol. 13 © 1989 Williams & Wilkins Co., Baltimore. Prepared by A.L. Usted. Photography by Dept. of Biophysics, Norwegian Institute of Technology

46. Extreme Habitats: Hot Springs
Biology, 9th ed,Sylvia Mader
Chapter 21
Viruses, Bacteria & Archaea
Extreme Habitats: Hot Springs
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
b(Main): © Jeff Lepore/Photo Researchers, Inc.; b (Inset): Courtesy Dennis W. Grogan, Univ. of Cincinnati

47. Extreme Habitats: Swamps
Biology, 9th ed,Sylvia Mader
Chapter 21
Viruses, Bacteria & Archaea
Extreme Habitats: Swamps
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
c(Main): © Susan Rosenthal/Corbis RM; c (Inset): © Ralph Robinson/Visuals Unlimited.