Bacteria and Viruses

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Bacteria and Viruses

• Chapter 19

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Bacteria Viruses
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19.1 Bacteria

• Come in many shapes and sizes
• Most common microorganisms are prokaryotes
• Average size of 1-5 micrometers
• Compared to eukaryotic cells that are 10-100
  micrometers in diameter

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2 Branches of Bacteria (Domains)

• Archebacteria (similar to early Earth)
• Confined to extreme environments
• Methanogens - reduce CO2 to CH4
• Extreme halophiles - salt loving
• Thermoacidophiles
• Similar to early earth
• More closely related to eukaryotes than to modern
  bacteria
• Eubacteria (most modern)
• very diverse

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Bacterial Classification
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Prokaryotic Phylogeny
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Prokaryotic Eukaryotic Cells
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Classifying Prokaryotes

• Eubacteria
• Largest prokaryote Domain
• Lack nuclei
• Cell wall of a carbohydrate- Peptidoglycan
• Cell membrane around cytoplasm
• Some have an extra cell wall on the outside to
  resist damage

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Classifying Prokaryotes

• Archaebacteria
• Lack nuclei
• Have cell walls without peptidoglycan
• Are chemically different from Eubacteria
• Many live in extremely harsh environments

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Bacteria Shapes
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Identifying Prokaryotes

• Shapes
• Bacilli- Rod shaped
• Cocci- Spherical shaped
• Sprilla- spiral shaped

Colorized SEM 12,000?
Colorized SEM 9,000?
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Identifying Prokaryotes

• Cell walls
• Gram staining used to tell them apart
• Gram bacteria look purple
• Gram- bacteria look pink

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The Bacterial Cell Wall

• Instead of cellulose, contain peptidoglycan
• A polymer of modified sugars cross-linked with
  amino acids
• The gram stain distinguishes many disease causing
  bacteria based on the type of cell wall
• Many antibiotics work by attacking the bacterial
  cell wall

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The Gram Stain

• Gram () Purple
• accept gram stain
• have simpler cell walls with large amounts of
  peptidoglycan
• Gram (-) Pink
• do not stain
• have more complex cell walls with less
  peptidoglycan
• cell walls contain lipopolysaccharides
• are more likely to be pathogenic (cause disease)
• more resistant to antibiotics

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Cell Wall Gram Stain
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Gram () Gram (-)
Gram ()Purple Gram (-)Pink
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Identifying Prokaryotes

• Movement
• Flagella
• Lash, snake or spiral forward
• They do not move at all

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Motility (movement)

• About half are capable of directional movement.
• 3 mechanisms
• flagella - different from eukaryotes
• spiral shaped bacteria (spirochetes) have a
  filament that spirals around the cell under the
  outer sheath
• some bacteria secrete slimy chemicals glide
• Taxis
• movement toward or away from a stimulus
• many bacteria exhibit this form of movement

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Structures of Movement
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Structure of Prokaryotic Flagella
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Metabolic Diversity

• Heterotrophs
• Chemoheterotrophs must take in organic molecules
  for energy and carbon
• Photoheterotrophs Use sunlight for energy but
  need organic compounds for a carbon source

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Metabolic Diversity

• Autotrophs
• Chemoautotrophs perform chemosynthesis to make
  carbon from carbon dioxide. Does not require
  sunlight
• Photoautotrophs use light to convert carbon
  dioxide and water into carbon compounds and
  oxygen gas.

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Getting Energy

• Bacteria need a constant supply of energy
• Obligate aerobes- require constant supply of
  oxygen
• Obligate anaerobes- need no oxygen, for some
  oxygen will kill it
• Facultative anaerobes- survive with or with out
  oxygen

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Growth and Reproduction

• Binary fission (to split)
• Conjugation
• Spore formation

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Binary Fission
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Bacterial Conjugation
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Endospores (example Anthrax)

• Some bacteria form resistant cells called
  endospores (11,000 year old spores found)
• Resist extremes of temperature, pH, etc.

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Importance of Bacteria

• Only a minority cause disease
• Many are essential to life on earth
• Decomposers
• Break down dead matter
• Nitrogen Fixers
• Converts nitrogen into a form plants can use
• Humans use Bacteria
• Often live in symbiotic relationships with other
  organisms

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19.2 Viruses

• What is a virus?
• Particles of nucleic acid and proteins
• Core made up of DNA or RNA surrounded by a capsid
• Need to infect a
• living host to reproduce

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Viral Structure
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Bacteriophage
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Are Viruses Alive?

• Viruses contain nucleic acids proteins
• Viruses, by themselves, cannot make or use food,
  grow or reproduce
• Some scientists believe viruses were never
  independently living organisms
• Others believe viruses evolved from simple
  bacteria like mycoplasmas rickettsiae
• Another hypothesis viruses are genes that have
  escaped from the genomes of living cells
• Not much evidence to support any one of these

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Viral Infection

• Lytic Cycle
• Virus attaches to host cell
• Injects its DNA
• Host makes RNA from viral DNA
• Cell begins to make copies of virus
• New viruses form
• Host cell bursts

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Lytic Cycle of the T4 Phage
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Viral Infection

• Lysogenic Cycle
• Virus attaches to host cell
• Injects DNA
• Viral DNA incorporates itself into the host DNA
• Viral DNA can be dormant
• Once it becomes active, it follows the 4
  processes in the lytic cycle

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Lytic and Lysogenic Cycle (video)

• http//www.youtube.com/watch?vgU8XeqI7ytsfeature
  related

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Phage Lytic and Lysogenic Cycles
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Viral Infection

• Retrovirus Genetic information is RNA
• Produces DNA copy and creates a prophage
• Example
• HIV/AIDS

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19.3 Diseases Caused by Bacteria and
Viruses

• Pathogens- disease causing agents
• Bacterial Disease
• Viral Diseases

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Diseases Caused By Bacteria

• How does bacteria produce disease?
• Damage the cells and tissues by breaking down
  the cells for food
• Releasing toxins (poisons into the body)

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Preventing Diseases

• Vaccines
• Immunity
• Antibiotics

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Controlling Bacteria

• Sterilization
• Disinfectants
• Proper food storage

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Diseases Caused by Viruses

• Viruses disrupt the bodys normal equilibrium
• Cannot be treated with antibiotics
• Viruses can infect humans and plants

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Virus-like Particles (Viroids)

• Viroids- single stranded RNA molecule with no
  capsid
• They cause diseases in plants
• Infect cell and produce more viroids by
  disrupting the plant metabolism

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Virus-like Particles (Prions)

• Prions- contain only protein no DNA or RNA
• They cause diseases in animals and humans
• Prions clump and cause normal protein to clump
  with it- creating new prions

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Prion Action
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Chapter 19Viruses and BacteriaMultiple Choice
Practice Questions
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191

• Which characteristic distinguishes eubacteria
  from archaebacteria?
• Eubacteria lack peptidoglycan in their cell
  walls.
• Eubacteria contain peptidoglycan in their cell
  walls.
• Eubacteria lack a nucleus.
• Eubacteria do not possess mitochondria.

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191

• Which characteristic distinguishes eubacteria
  from archaebacteria?
• Eubacteria lack peptidoglycan in their cell
  walls.
• Eubacteria contain peptidoglycan in their cell
  walls.
• Eubacteria lack a nucleus.
• Eubacteria do not possess mitochondria.

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191

• Rod-shaped prokaryotes are called
• bacilli.
• cocci.
• spirilla.
• streptococci.

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191

• Rod-shaped prokaryotes are called
• bacilli.
• cocci.
• spirilla.
• streptococci.

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191

• Bacteria that must live without oxygen are called
  
• obligate aerobes.
• facultative anaerobes.
• obligate anaerobes.
• facultative aerobes.

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191

• Bacteria that must live without oxygen are called
  
• obligate aerobes.
• facultative anaerobes.
• obligate anaerobes.
• facultative aerobes.

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191

• Prokaryotes that make their own food molecules
  from carbon dioxide and water but live where
  there is no light are called
• photoautotrophs.
• photoheterotrophs.
• chemoautotrophs.
• chemoheterotrophs.

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• Prokaryotes that make their own food molecules
  from carbon dioxide and water but live where
  there is no light are called
• photoautotrophs.
• photoheterotrophs.
• chemoautotrophs.
• chemoheterotrophs.

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191

• Bacteria that attack and digest the tissue of
  dead organisms are called
• decomposers.
• nitrogen fixers.
• chemoautotrophs.
• archaebacteria.

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191

• Bacteria that attack and digest the tissue of
  dead organisms are called
• decomposers.
• nitrogen fixers.
• chemoautotrophs.
• archaebacteria.

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192

• Viruses that contain RNA as their genetic
  information are known as
• prions.
• oncoviruses.
• retroviruses.
• bacteriophage.

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192

• Viruses that contain RNA as their genetic
  information are known as
• prions.
• oncoviruses.
• retroviruses.
• bacteriophage.

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192

• The first type of virus to be studied was the
• bacteriophage.
• tobacco mosaic virus.
• influenza virus.
• AIDS virus.

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192

• The first type of virus to be studied was the
• bacteriophage.
• tobacco mosaic virus.
• influenza virus.
• AIDS virus.

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192

• Which of the following statements about viruses
  is true?
• Viruses appear similar to bacteria when studied
  with a light microscope.
• Viruses display the essential characteristics of
  living things.
• Viruses can reproduce independently if they
  contain DNA.
• Viruses cannot reproduce unless they infect a
  living cell.

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192

• Which of the following statements about viruses
  is true?
• Viruses appear similar to bacteria when studied
  with a light microscope.
• Viruses display the essential characteristics of
  living things.
• Viruses can reproduce independently if they
  contain DNA.
• Viruses cannot reproduce unless they infect a
  living cell.

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• A virus integrates its DNA into the DNA of the
  host cell but remains inactive for a while in
• a lytic infection.
• a lysogenic infection.
• neither a lytic nor a lysogenic infection.
• retroviral infection.

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• A virus integrates its DNA into the DNA of the
  host cell but remains inactive for a while in
• a lytic infection.
• a lysogenic infection.
• neither a lytic nor a lysogenic infection.
• retroviral infection.

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• Retroviruses are considered unique because
• they have RNA in their capsid and not DNA.
• they have DNA in their capsid and not RNA.
• after infection of a host cell, their RNA makes
  DNA.
• after infection of a host cell, their DNA makes
  RNA.

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192

• Retroviruses are considered unique because
• they have RNA in their capsid and not DNA.
• they have DNA in their capsid and not RNA.
• after infection of a host cell, their RNA makes
  DNA.
• after infection of a host cell, their DNA makes
  RNA.

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193

• Biologists know that bacteria can cause human
  disease by
• entering cells and using the cell to make new
  bacteria.
• producing toxic substances that interfere with
  normal cell functi
• decomposing the remains of dead organisms.
• changing atmospheric nitrogen into nitrogen
  compounds.

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• Biologists know that bacteria can cause human
  disease by
• entering cells and using the cell to make new
  bacteria.
• producing toxic substances that interfere with
  normal cell functio
• decomposing the remains of dead organisms.
• changing atmospheric nitrogen into nitrogen
  compounds.

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• A process that destroys bacteria by subjecting
  them to great heat is known as
• refrigeration.
• sterilization.
• pickling.
• boiling.

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193

• A process that destroys bacteria by subjecting
  them to great heat is known as
• refrigeration.
• sterilization.
• pickling.
• boiling.

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• Which of the following diseases is transmitted by
  a mosquito bite?
• influenza
• measles
• West Nile virus
• chickenpox

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• Which of the following diseases is transmitted by
  a mosquito bite?
• influenza
• measles
• West Nile virus
• chickenpox

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• Which of the following diseases is thought to be
  caused by prions?
• diphtheria
• mad cow disease
• tuberculosis
• smallpox

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• Which of the following diseases is thought to be
  caused by prions?
• diphtheria
• mad cow disease
• tuberculosis
• smallpox

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• The best way to combat viral diseases is
• to use antibiotics.
• to treat individual symptoms.
• to use preventive vaccines.
• to let the disease cure itself.

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• The best way to combat viral diseases is
• to use antibiotics.
• to treat individual symptoms.
• to use preventive vaccines.
• to let the disease cure itself.