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Chapter 19: Bacteria and Viruses

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Title: Chapter 19: Bacteria and Viruses


1
Chapter 19 Bacteria and Viruses
2
Viruses
  • Means poison in Latin
  • Nonliving
  • Composed of nucleic acids enclosed in a protein
    coat
  • Smaller than bacteria (can vary in structure and
    size)
  • Can only replicate
  • Make copies of itself
  • Need a host/living cell to reproduce
  • No cell respiration, growth, response to stimuli
  • Not considered a living cell

3
1935 W. Stanley
  • 1st to identify a virus
  • Tobacco Mosaic Virus

4
Structure of a Virus
  • Inner core of nucleic acid (DNA or RNA)
  • Outer protein coat called a capsid
  • Gives virus its shape
  • Some viruses have a membrane (envelope) over the
    capsid
  • Can have spikes, hooks, etc.

5
Bacteriophage
  • Special group of viruses
  • Infect bacteria
  • Inject their nucleic acid into bacteria like a
    syringe

6
Viruses are classifies by the type of host they
infect
  • Plant viruses
  • Animal viruses
  • Bacterial viruses

7
Viruses are often species-specific
  • Some are cell-type specific
  • Ex cold viruses? affect respiratory cells
  • Ex Polio virus ? affects nerve cells

8
2 Types of Reproduction
  • Lytic cycle (short) takes about 30 minutes to
    produce 200 new viruses
  • Virus enters cell ? reproduces ? exits cell
  • Kills host cell causes host cell to break open
  • Steps ex cold virus
  • attachment
  • entry
  • replication
  • assembly
  • lysis and release

9
Lysogenic Cycle (long)
  • Virus has an inactive (dormant) period
  • Steps ex herpes, HIV, and chickenpox
  • attachment and entry
  • provirus formation (prophage)
  • viral DNA integrated into hosts chromosomes
  • normal cell activity
  • activation of the lytic cycle

10
Retrovirus
  • RNA virus with the enzyme reverse transcriptase
  • Makes viral DNA from host cell RNA
  • Ex HIV

11
Fighting Viruses
  • Natural defenses
  • Skin, mucus membranes, white blood cells,
    antibody production, interferon
  • Vaccines
  • Preparation of weakened or killed virus/viral
    proteins
  • Some produce life-long specific antibodies
  • Antibiotics do not kill viruses

12
How Viruses are Spread
  • Air (measles, cold)
  • Food and water (hepatitis)
  • Animal/insect bites (rabies, encephalitis)
  • Insects (flies can carry viruses)
  • Sexual contact (HIV, Herpes)
  • 1st line of defense ? skin and membranes

13
Chapter 19 Review 1
  • A typical virus has a core composed of ___.
  • a. capsid proteins c. membrane envelopes
  • b. surface proteins d. DNA or RNA
  • 2. The outer layer of a virus is composed of
    ____.
  • a. RNA b. viral genes c. DNA d. proteins
  • 3. A(an) _____ is a preparation of weakened or
    killed pathogens that can prompt the body to
    produce immunity to a disease.

14
Bacteria
  • Prokaryotic
  • Unicellular organisms
  • Have no nucleus
  • No membrane-bound organelles

15
Divided into 2 Kingdoms
  • Archaebacteria
  • Live in extreme habitats (usually no oxygen
    present)
  • Cell walls lack peptidoglycan (starch)
  • 3 types
  • Methanogens
  • Produce methane gas
  • Live in marshes, lake sediments, and cow
    digestive tracts
  • Found at sewage disposal plants to help break
    down sewage

16
Extreme Halophiles
  • Lives only in places where there is a high salt
    concentration
  • Found in Utahs Great Salt Lakes and the Dead Sea

17
Thermoacidophiles
  • Lives in hot, acidic waters of sulfur springs
  • Found in volcanic vents

18
Eubacteria
  • Live almost everywhere
  • Cell walls made of peptidoglycan
  • Divided up based on how they get their food
  • Autotrophs
  • Make their own food
  • 2 types
  • Photosynthetic
  • Need sunlight
  • Ex cyanobacteria (blue-green algae)
  • Chemosynthetic
  • Use sulfur and nitrogen to make food

19
Eubacteria
  • Heterotrophs
  • Use others/consumes to get food
  • 2 ways
  • Parasitism, mutualism, commensalism
  • Gets food from other living things
  • Saprophytes
  • Feed on dead organisms/wastes
  • Decomposers

20
Structure of Bacteria
  • Very small in size
  • All have Some have
  • DNA Pili
  • Cell membrane Capsule
  • Cell wall Flagella
  • Ribosomes
  • Genes are in a big circular chromosome (not
    paired chromosomes)

21
  • Cell wall keeps bacteria from bursting
  • Most bacteria live in a hypotonic environment
  • 1928 Alexander Fleming
  • Accidentally discovered Penicillin
  • 1st antibiotic
  • Destroys bacteria by interfering with its ability
    to make a cell wall

22
Identifying Bacteria
  • Gram Staining
  • Based on differences in a bacteriums cell wall
  • Gram positive will stain a blue/purple color
  • Gram negative will stain a pink color

23
Shapes of Bacteria
  • Bacteria have 3 shapes
  • Cocci sphere-shaped
  • Bacilli rod-shaped
  • Spirilla spiral-shaped

24
Bacteria can grow in patterns
  • Diplo- arranged in pairs
  • Staphylo- cells arranged like grapes
  • Strepto- arrangement of chains of cells

25
Asexual Reproduction
  • Binary Fission
  • Exponential growth 1?2?4?8?16?32etc
  • Very fast (every 20 minutes)
  • Cells produced are genetically identical

26
Sexual Reproduction
  • Called conjugation
  • DNA is exchanged through structures called pili
    that connect cells together

27
Metabolism
  • Breaking down food to release energy
  • 3 groups of bacteria based on way they
    metabolize
  • Obligate aerobes require oxygen
  • Ex Mycobacterium tuberculosis

28
  • Facultative anaerobes can live with or without
    oxygen
  • Ex E. coli

29
  • Obligate anaerobes die in the presence of oxygen
  • Ex Clostridium, Treponema

30
Importance of Bacteria
  • Help fertilize fields
  • Recycles nutrients breakdown dead
    materials/waste (called saprophytes)
  • Produce foods and medicines/antibiotics
  • Nitrogen fixation makes a usable form of nitrogen

31
Harmful Bacteria called pathogens
  • Can cause disease in plants and animals
  • Interferes with normal body function
  • Affects homeostasis
  • Can release a toxin that attacks the host (like a
    poison)

32
Survival Adaptations
  • Produce endospores
  • Contain bacterial DNA and cytoplasm
  • Covered with a tough, outer case that resists
    temperature extremes, drying out, and harsh
    chemicals
  • Dormant resting state (can be as long as 1,000
    years)
  • Does not reproduce during this time
  • Can germinate when environmental conditions
    improve
  • Must be exposed to high heat under pressure to be
    killed
  • Called sterilization

33
Chapter 19 Review 2
  • A ______ is a disease-causing agent.
  • 2. List 4 ways to identify prokaryotes.
  • 3. One way to control bacterial growth is by
    subjecting them to great heat, a process called
    _____.
  • 4. Bacteria can also cause disease by releasing
    ______ that harm the body.
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