Ch. 19 Bacteria and Viruses

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Ch. 19 Bacteria and Viruses
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Ch. 19 Outline

• 19-1 Bacteria
• Classifying prokaryotes
• Identifying Prokaryotes
• Metabolic Diversity
• Growth and Reproduction
• Importance of Bacteria

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Bacteria

• Once microscopes were invented, scientists
  discovered a world of microorganisms.
• The smallest and most common microorganisms are
  the prokaryotes, which are single-celled
  organisms that lack a nucleus
• The word bacteria is so familiar, that we will
  use it as a common term to describe prokaryotes

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Ch. 19 Outline

• 19-2 Viruses
• What is a virus?
• Viral Infection
• Retroviruses
• Viruses and Living Cells
• 19-3 Diseases caused by bacteria and viruses
• Bacterial Diseases in Humans
• Controlling Bacteria
• Viral Diseases
• Viroids and Prions

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Bacteria

• Prokaryotes range in size from 1 to 5 micrometers
  in diameter. There are exceptions to this rule.
  The Epulopiscium fisheloni is about 500
  micrometers long.

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Classifying Prokaryotes

• All prokaryotes were once classified in a single
  Kingdom named Monera.
• Two Kingdoms of bacteria Eubacteria,
  Archaebacteria
• Some scientists think that the Eubacteria and
  Archaebacteria should be classified as Domains.

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Classifying Prokaryotes

• Eubacteria the larger of the two kingdoms
• Some live in fresh water, salt water, land, on
  and within the human body. They can infect large
  animals
• Eubacteria cell walls protects the cell from
  injury and determines its shape
• Eubacteria cell walls contain peptidoglycan, a
  carbohydrate
• Inside the cell wall, a cell membrane protects
  the cytoplasm of eubacteria. Some eubacteria
  have a second cell membrane outside the cell
  membrane

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Classifying Prokaryotes

• Archaebacteria are similar to Eubacteria in that
  they are equally small, lack nuclei, and have
  cell walls
• Archaebacteria do not have peptidoglycan in their
  cell walls, plus they have different membrane
  lipids
• Also, the DNA sequences of key archaebacteria are
  more like those of eukaryotes than those of
  eubacteria
• archaebacteria may possibly be ancestors of
  eukaryotes

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tainano.com
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Classifying Prokaryotes

• Many archaebacteria live in harsh environments.
  One group of arcaheabacteria is the methanogens,
  that produce methane gas.
• Methanogens Use only CO2, H and N to produce
  energy to live, and as a result give off methane
  gas.
• Live in swamps, marshes, gut of cattle, termites,
  etc.
• Methanogens are decomposers
• Other archaebacteria live in
• extremely salty environments or in
• hot springs, mud or digestive tracts
• of animals

www.biology.iupui.edu/.../N100/2k23domain.html
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Classifying Prokaryotes
Bacteria
are classified into the kingdoms of
live in harsh environments such as
include a variety of lifestyles such as
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Classifying Prokaryotes
Bacteria
are classified into the kingdoms of
live in harsh environments such as
include a variety of lifestyles such as
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Identifying Prokaryotes Shapes

• Prokaryotes are identified by
• Their shape
• The chemical nature of cell walls
• The way they move

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Identifying Prokaryotes Shapes

• Rod-shaped prokaryotes are called bacilli
• Spherical shaped prokaryotes are called cocci
• Spiral and corked-shaped prokaryotes are called
  spirilla

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Identifying Prokaryotes Cell Walls

• Two different types of cell walls are found in
  Eubacteria
• A method called Gram staining is used to tell the
  two different types of cell walls apart
• Violet stain is used to stain the peptidoglycan
  cell walls
• Alcohol treatment may wash away the violet stain.
  If the violet stain remains, then the bacteria
  are said to be Gram-positive
• These bacteria have thick peptidoglycan cell
  walls

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Identifying Prokaryotes Cell Walls

• Gram-negative bacteria have much thinner cell
  walls inside an outer lipid layer
• Alcohol dissolves the lipid and removes the
  violet stain from the cell walls. The
  counterstain makes these bacteria appear pink

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Identifying Prokaryotes Cell Walls

• What does the type of cell wall have to do with a
  bacteriums resistance to antibiotics?
• Gram negative bacterias extra layer outside the
  cell wall can make it hard for some antibiotics
  to get inside the cell (where they can work).
• That makes it important for a doctor to know what
  kind of bacteria is causing the infection so that
  most effective antibiotic can be used to treat it.

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Identifying Prokaryotes Movement

• How are the ways prokaryotes move?
• Some do not move
• Propelled by flagella
• Lash snake or spiral forward
• Glide
• Which characteristic of prokaryotes illustrates
  their diversity best?
• By the way they obtain energy

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Identifying Prokaryotes Metabolic Diversity

• Which characteristic of prokaryotes illustrates
  their diversity best?
• By the way they obtain energy
• Most prokaryotes are heterotrophs, meaning they
  get their energy by consuming organic molecules
  made by organisms
• Other prokaryotes are autotrophs and make their
  own food from inorganic molecules

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Identifying Prokaryotes Metabolic Diversity

• Most heterotrophic prokaryotes must take in
  organic molecules for both energy and a source of
  carbon. These are called chemoheterotrophs.
• Humans are also chemoheterotrophs
• If human food is not handled carefully, bacteria
  may eat our food and release toxins that cause
  food poisoning

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Identifying Prokaryotes Metabolic Diversity

• Photoautotrophs use light energy to convert
  carbon dioxide and water to carbon compounds and
  oxygen
• Photoautotrophs are found where light is
  plentiful
• The photoautrophs Cyanobacteria contain a bluish
  pigment and chlorophyll. They are found
  everywhere (land, salt and fresh water) and are
  the first to recolonize an area after a natural
  disaster.

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Identifying Prokaryotes Metabolic Diversity

• Chemoautotrophs perform chemosynthesis.
• They make organic carbon molecules from carbon
  dioxide.

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Identifying Prokaryotes Metabolic Diversity

• Chemoautotrophs do not require light as a source
  of energy. Instead, they use energy directly
  from chemical reactions involving ammonia,
  hydrogen sulfide, nitrites, sulfur or iron
• Some live deep in the darkness of the ocean
• They use hydrogen sulfide gas that flows from
  hydrothermal vents in the ocean

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Identifying Prokaryotes Metabolic Diversity

• Like all organisms, bacteria need a constant
  supply of energy. This energy is released by the
  process of cellular respiration or photosynthesis
  or both
• Organisms that require a constant supply of
  oxygen to live are called Obligate Aerobes
• Obligate Anerobes DO NOT REQUIRE oxygen and may
  be killed by it

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Clostridium botulinum
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Clostridium botulinum

• Obligate Anerobe found in soil
• Gram positive
• Rod-shaped
• Grow in can foods that have not been properly
  sterilized

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• Faculative Anerobes can live with or without
  oxygen
• Faculative anerobes can live anywhere because
  they can switch between the processes of cellular
  respiration or fermentation depending on their
  environment

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Escherichia Coli (E. Coli)
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Escherichia Coli (E. Coli)

• Faculative anerobe
• Gram negative
• Rod shaped
• Lives anerobically in large intestine
• Lives aerobically in sewage or contaminated water

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Escherichia Coli (E. Coli)

• Eschericha coli are normal inhabitants of our
  digestive tract
• A new strain of E. coli (O157H7) has caused
  illness and death for people who ate contaminated
  hamburger meat.

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Growth and Reproduction

• Bacteria can not grow and divide indefinitely
  because of the availability of food and they have
  to get rid of wastes
• Bacteria grow and divide very rapidly. Their
  method of division is called binary fission
• Bacteria grow until they double in size, copies
  DNA and simply splits into two daughter cells
• Binary fission is just asexual reproduction (no
  exchange of genetic material)

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Binary Fission
http//www.swt.edu/rr33/
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Growth and Reproduction

• Conjugation A process of exchanging genetic info
  in bacteria
• A hollow bridge forms between two bacterial cells
  and genes move from one cell to the other
• Increases genetic diversity of bacteria

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Growth and Reproduction

• When growth conditions become unfavorable, many
  bacteria produce spores, which can remain dormant
  until there are more favorable growth conditions.
• Endospore one type of spore formed when a
  bacterium produces a thick internal wall that
  encloses its DNA and a portion of its cytoplasm.

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Importance of Bacteria

• We could not survive without bacteria. Some are
  producers, others are decomposers, and some are
  used by humans for various things.

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Endospores
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Importance of Bacteria

• We could not survive without bacteria. Some are
  producers, others are decomposers, and some are
  used by humans for various things.
• Decomposers
• Bacteria help recycle nutrients in the
  environment
• Attack and digest dead tissue
• Break down complex compounds in sewage to
  simpler ones
• Produce purified water
• Produce nitrogen and carbon dioxide gases
• Produce fertilizer compounds

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Importance of Bacteria

• Nitrogen Fixers
• PLANTS NEED NITROGEN TO MAKE AMINO ACIDS which
  are used to make PROTEINS
• Plants can not use nitrogen gas (N2) directly.
  Nitrogen must first be changed chemically to
  ammonia (NH3) or other nitrogen compounds. The
  process of converting nitrogen gas to a form that
  plants can use is called nitrogen fixation.
• Many plants have symbiotic relationships with
  nitrogen-fixing bacteria. The bacterium
  Rhizobium, grows on the roots of soybean plants.
  The plant provides nutrients for Rhizobium, and
  it converts nitrogen gas in the air to ammonia,
  which helps the plant.

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Importance of Bacteria

• Human Uses of Bacteria
• Produce a wide variety of food and beverages
• Industry ? cleaning up oil spills (digest
  petroleum)
• Mine minerals from the ground
• Remove wastes and poisons from water
• Synthesize drugs and chemicals (genetic
  engineering)
• Produce vitamins in human intestines
• Produce heat stable enzymes that can be used in
  medicine, food production, and industrial
  chemistry

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Ch. 19 Outline

• 19-2 Viruses
• What is a virus?
• Viral Infection
• Retroviruses
• Viruses and Living Cells

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What is a Virus?

• The word virus is derived from the Latin word for
  poison
• Dmitri Ivanovski identified the cause of tobacco
  mosaic disease by extracting juice from an
  infected plant
• Martinus Beijerinck suggested that tiny particles
  in the extracted juice caused tobacco mosaic
  disease (called particles viruses)
• Wendell Stanley inferred that viruses were not
  alive when he obtained crystals of tobacco mosaic
  virus

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What is a Virus?

• The word virus is derived from the Latin word for
  poison
• Viruses particles of nucleic acids, proteins and
  in some cases, lipids
• Viruses are NON-LIVING, but they do reproduce.
• Viruses can reproduce only by infecting living
  cells and once inside, they use the machinery of
  the infected cell to produce more viruses

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Viral Structures
A typical virus is composed of a core of DNA or
RNA surrounded by a protein coat.
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What is a Virus?

• The simplest virus may have only a few genes,
  whereas the most complex may have more than a
  hundred genes
• A viruses protein coat is called its capsid. The
  capsid includes proteins that enable a virus to
  enter a host cell.
• The capsid proteins of a typical virus bind to
  receptors on the surface of a cell and trick
  the cell into allowing it inside.

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What is a Virus?

• Once inside, the viral genes are expressed. The
  cell transcribes and translates the viral genetic
  information into viral capsid proteins
• Sometimes the genetic program causes the host
  cell to make copies of the virus, and in the
  process the host cell is destroyed.

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What is a Virus?

• Viruses must bind precisely to proteins on the
  cell surface and then use the hosts genetic
  system
• Viruses that infect bacteria are called
  bacteriophages

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Viral Infection

• There are two types of viral infections lytic
  and lysogenic
• Lytic Infection
• The virus enters the cell, makes copies of
  itself, and causes the cell to burst (destroyed)
• In a lytic infection, the protein capsid is
  activated by contact with a specific host cell
• It then injects its DNA directly into the host
  cell.
• The host cell cannot tell the difference between
  its own DNA and the DNA of the virus

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Viral Infection

• Consequently, the cell begins to make messenger
  RNA from the genes of the virus
• This viral mRNA is translated into viral proteins
  that act like a molecular wrecking crew, chopping
  up the cell DNA, a process that shuts down the
  infected host cell
• In this lytic infection, the virus then uses the
  materials of the host cell to make thousands of
  copies of its own DNA molecule

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Viral Infection

• The viral DNA gets assembled into new virus
  particles
• Before long, the infected cell lyses or bursts,
  and releases hundreds of virus particles that
  may go on to infect other cells
• Because the host cell is lysed and DESTROYED,
  this process is called a lytic infection

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Viral Infection

• Lysogenic Infection
• A host cell makes copies of the virus
  indefinitely
• A virus incorporates its DNA into the DNA of the
  host cell, and the viral genetic information
  replicates along with the host cells DNA
• Lysogenic viruses do not lyse the host cell
  right away. A lysogenic virus remains inactive
  for a period of time

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Viral Infection

• The viral DNA that is embedded in the hosts DNA
  is called a prophage
• The prophage may remain part of the DNA of the
  host cell for many generations before it becomes
  active.
• Eventually, from any number of factors, the DNA
  of a prophage will be activated. It will remove
  itself from the host cell DNA and direct the
  synthesis of new virus particles

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Lytic Vs. Lysogenic
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Retroviruses

• Retroviruses viruses that have RNA as their
  genetic material.
• When a retroviruses infect a cell, they produce a
  DNA copy of their RNA. This DNA, much like a
  prophage, is incorporated into the DNA of the
  host cell.
• There the retrovirus may remain dormant for
  varying lengths of time before becoming active

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Retroviruses

• Retroviruses get their name from the fact that
  their genetic information is copied backwards,
  that is from RNA to DNA instead of from DNA to
  RNA.
• The prefix retro means backwards
• The virus that causes acquired immune deficiency
  syndrome (AIDS) is a retrovirus and some cancers
  are caused by retroviruses

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Figure 18.9 The structure of HIV, the retrovirus
that causes AIDS
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Figure 18.10 The reproductive cycle of HIV, a
retrovirus
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Viruses and Living Cells

• Viruses must infect a living cell in order to
  grow and reproduce
• Viruses take advantage of the hosts respiration,
  nutrition, and all other functions and are
  therefore parasites
• Viruses are not alive because they are not made
  up of cells and are able to live independently

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Viruses and Living Cells

• Yet viruses can reproduce, regulate gene
  expression and even evolve after infecting living
  cells
• Viruses are at the borderline of living and
  non-living things

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Viruses and Living Cells

• Viruses were not probably the first living things
  because they are completely dependent on living
  things
• Viruses may have evolved from the genetic
  material of living things

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Ch. 19 Outline

• 19-3 Diseases caused by bacteria and viruses
• Bacterial Diseases in Humans
• Controlling Bacteria
• Viral Diseases
• Viroids and Prions

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Bacterial Diseases in Humans

• Pathogen disease-causing agents
• Disease can be considered a conflict between the
  pathogen and the host
• Louis Pasteur was the first scientist to show
  that bacteria cause a number of human and animal
  diseases (The Germ Theory)

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Bacterial Diseases in Humans

• Bacteria produce disease in one of two ways
• Damage the cells and tissue of the infected
  organism by directly breaking down the cells for
  food
• Release toxins (poisons) that travel throughout
  the body and interfere with normal activity of
  the host.

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• The gram positive bacterium Mycobacterium
  tuberculosis is inhaled into the lungs where it
  destroys lung tissue
• If bacterium enters a blood vessel, it may travel
  to new sights and destroy more tissue

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• The Gram positive strain of the Streptococcus
  bacterium from Group A causes strep throat by
  releasing toxins into the blood stream
• This infection can also cause damage to the heart
  valves (rheumatic fever) and kidneys (nephritis).
  Streptococcal infections can also cause scarlet
  fever, tonsillitis, pneumonia, sinusitis and ear
  infections.

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• The Gram positive bacterium Corynebacterium
  diptheria which causes diptheria infects the
  tissues of the throat and releases toxins into
  the blood stream
• Diptheria can lead to breathing problems, heart
  failure, paralysis, and death

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Preventing bacterial disease

• Vaccine preparation of weakened or killed
  pathogen
• Prompts bodys immune system and promts the body
  to produce immunity to the disease
• Immunity is the bodys ability to destroy new
  pathogens
• Antibiotics compounds that block the growth and
  reproduction of bacteria

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Antibiotics

• Antibiotic-resistant bacteria bacteria that
  have mutated that make them no longer susceptible
  to the effects of antibiotics
• Genetic mutations for antibiotic resistance
  happen spontaneously as a result of errors in DNA
  replication
• Taking Antibiotics eliminates the susceptible
  bacteria from the body and leaves the resistant
  bacteria, allowing them to reproduce and pass on
  their genetic traits (bacteria reproduce very
  rapidly!!!)

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Antibiotics

• Antibiotic misuse
• Usually, if a full course of an Antibiotic is
  taken, all the targeted bacteria are killed and
  there is no chance for a resistant strain to
  evolve
• but if the antibiotic is stopped early, the
  surviving bacteria will be the ones that were
  most resistant to the antibiotic

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Antibiotics

1. There are now strains of tuberculosis and S.
   aureus that are resistant to multiple drugs
   hard to treat! (Multiple Drug Resistant Bacteria)
2. Widespread use of antibacterial soaps can cause
   antibiotic resistant strains of bacteria to evolve

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• Bacillus Anthracis (Anthrax)
• Gram positive
• Forms endospores
• Found in soil or on the fur of animals or in
  their digestive tracts
• Dangerous to humans and animals
• Lung, intestines, and skin
• Respiratory difficulties, fever, diarrhea, rash

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Food Poisoning

• Staphylococcus aureus
• Gram positive
• causes the most common type of food poisoning
• painful diarrhea and vomiting

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Food Poisoning

• Salmonella bacteria (from unprocessed milk,
  pork, poultry, eggs)
• Gram negative
• cause vomiting, nausea, and stomach cramps, which
  can lead to fever and death (especially in the
  very young or very old)

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Bacteria Table
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Preventing bacterial disease

• Controlling Bacteria
• There are various methods used to control
  bacterial growth
• Sterilization kills pathogenic bacteria with heat
• Disinfectants are chemical solution that kills
  pathogenic bacteria
• Overuse of disinfectants increase the likelihood
  that common bacteria will eventually evolve to
  become resistant to them and therefore much
  more dangerous and difficult to kill

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Preventing bacterial disease

• Controlling Bacteria
• Food processing allows storage of food in
  refrigerators to prevent (delay) spoilage, or
  cooking of food at high enough temperatures to
  kill pathogens
• Canning preserves food for a long time. Food is
  heated to a high temperature and placed in
  sterile glass jars or metal containers and
  sealed. Food that has been properly canned will
  last almost indefinitely.
• Treating food with everyday chemicals such as
  salt (salted meat), vinegar (pickled vegetables),
  or sugar (jam) will preserve food.

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Viral Disease in Humans

• Like bacteria, viruses produce disease by
  disrupting the bodys normal equilibrium.
• Viruses may destroy cells they infect or cause
  infected cells to alter their growth and
  development
• Unlike bacteria, viral diseases cannot be treated
  with antibiotics, but there are some vaccines
  against viruses. Vaccines should be used before
  an infection begins

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Viral Disease in Humans

• Oncogenic or tumor causing viruses may produce
  cancer by disrupting the normal controls over
  cell growth and division
• Rous Sarcoma Virus in chickens
• Human Papilloma Virus genital warts cervical
  cancer

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Viral Disease in Humans

• Hepatitis B Virus Liver cancer
• Epstein-Barr Virus (the virus that causes mono
  or even chronic fatigue syndrome) Burkitts
  lymphoma

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Viral Disease in Plants

• Plant viruses pose a serious threat to the foods
  we eat
• Viruses have a hard time entering plant cells
  because plant cells have a tough cell wall
• Viruses enter plants through tears in leaf
  tissues, breaks in stems or roots, or
  microscopic cell wall damage
• Most plant viruses are spread by feeding action
  of insects

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Virus Disease Table
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Viroids and Prions

• Scientists have discovered two other virus-like
  particles that also cause disease Viroids and
  Prions
• Viroids cause disease in plants
• Prions cause disease in animals
• Viroids Single-stranded RNA molecules that have
  no surrounding capsids
• Affect _______ Cells

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Viroids and Prions

• Viroids Single-stranded RNA molecules that have
  no surrounding capsids
• It is believed that viroids enter an infected
  cell and direct the synthesis of new viroids
• The viroids then disrupt the metabolism of the
  plant cell and stunt the growth of the entire
  plant

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Prions

• Prions contain no DNA or RNA only protein
• Disease-causing proteins are folded into the
  wrong shape, which does not allow it to function
  as it should.
• If a normal prion comes into contact with a
  disease-causing one, the normal one will also
  change its shape so that it is folded wrong and
  no longer functions either in this way, the
  disease spreads
• Diseases such as Scrapie (sheep), mad cow
  disease, Creutzfeldt-Jacob disease (in humans)
  are all prion diseases that can be distributed by
  eating meat that contains the malfolded prion.

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Prions