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Ch. 19 Bacteria and Viruses

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Title: Ch. 19 Bacteria and Viruses


1
Ch. 19 Bacteria and Viruses
2
Ch. 19 Outline
  • 19-1 Bacteria
  • Classifying prokaryotes
  • Identifying Prokaryotes
  • Metabolic Diversity
  • Growth and Reproduction
  • Importance of Bacteria

3
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

4
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

5
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.

6
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.

7
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

8
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

9
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10
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
11
Classifying Prokaryotes
Bacteria
are classified into the kingdoms of
live in harsh environments such as
include a variety of lifestyles such as
12
Classifying Prokaryotes
Bacteria
are classified into the kingdoms of
live in harsh environments such as
include a variety of lifestyles such as
13
Identifying Prokaryotes Shapes
  • Prokaryotes are identified by
  • Their shape
  • The chemical nature of cell walls
  • The way they move

14
Identifying Prokaryotes Shapes
  • Rod-shaped prokaryotes are called bacilli
  • Spherical shaped prokaryotes are called cocci
  • Spiral and corked-shaped prokaryotes are called
    spirilla

15
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

16
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

17
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.

18
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

19
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

20
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

21
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.

22
Identifying Prokaryotes Metabolic Diversity
  • Chemoautotrophs perform chemosynthesis.
  • They make organic carbon molecules from carbon
    dioxide.

23
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

24
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

25
Clostridium botulinum
26
Clostridium botulinum
  • Obligate Anerobe found in soil
  • Gram positive
  • Rod-shaped
  • Grow in can foods that have not been properly
    sterilized

27
  • 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

28
Escherichia Coli (E. Coli)
29
Escherichia Coli (E. Coli)
  • Faculative anerobe
  • Gram negative
  • Rod shaped
  • Lives anerobically in large intestine
  • Lives aerobically in sewage or contaminated water

30
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.

31
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)

32
Binary Fission
http//www.swt.edu/rr33/
33
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

34
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.

35
Importance of Bacteria
  • We could not survive without bacteria. Some are
    producers, others are decomposers, and some are
    used by humans for various things.

36
Endospores
37
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

38
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.

39
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

40
Ch. 19 Outline
  • 19-2 Viruses
  • What is a virus?
  • Viral Infection
  • Retroviruses
  • Viruses and Living Cells

41
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42
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

43
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

44
Viral Structures
A typical virus is composed of a core of DNA or
RNA surrounded by a protein coat.
45
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.

46
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.

47
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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

49
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

50
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

51
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

52
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

53
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

54
Lytic Vs. Lysogenic
55
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

56
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

57
Figure 18.9 The structure of HIV, the retrovirus
that causes AIDS
58
Figure 18.10 The reproductive cycle of HIV, a
retrovirus
59
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

60
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

61
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

62
Ch. 19 Outline
  • 19-3 Diseases caused by bacteria and viruses
  • Bacterial Diseases in Humans
  • Controlling Bacteria
  • Viral Diseases
  • Viroids and Prions

63
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)

64
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.

65
  • 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

66
  • 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.

67
  • 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

68
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

69
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!!!)

70
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

71
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

72
  • 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

73
Food Poisoning
  • Staphylococcus aureus
  • Gram positive
  • causes the most common type of food poisoning
  • painful diarrhea and vomiting

74
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)

75
Bacteria Table
76
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

77
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.

78
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

79
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

80
Viral Disease in Humans
  • Hepatitis B Virus Liver cancer
  • Epstein-Barr Virus (the virus that causes mono
    or even chronic fatigue syndrome) Burkitts
    lymphoma

81
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

82
Virus Disease Table
83
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

84
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

85
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
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