KEY CONCEPT Infections can be caused in several ways.

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KEY CONCEPT Infections can be caused in several
ways.
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Any disease-causing agent is called a pathogen.
1 nanometer (nm) one billionth of a meter
100 nm
eukaryotics cells10,000-100,000 nm
viroids5-150 nm
viruses50-200 nm
prokaryotics cells200-10,000 nm
prion2-10 nm
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• A prion is made only of proteins.

• Causes misfolding of other proteins
• Results in diseases of the brain

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• A Virus is made of DNA or RNA and a protein coat.

• Non-living pathogen
• Can infect many organisms
• A Viroid is made only of single-stranded RNA
• Causes disease in plants
• Passed through seeds or pollen

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Characteristics of Viruses
18.2 Viral Structure and Reproduction

• NO - nucleus, cytoplasm, organelles, or cell
  membrane
• NOT capable of carrying out cellular functions
• NOT alive!

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Viruses
18.2 Viral Structure and Reproduction

• Obligate Intracellular parasites - depend on host
  cells for replication
• Spread by wind, water, food, blood or other
  bodily secretions
• Named for the disease they cause or the tissue
  they infect

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Viral Structure
18.2 Viral Structure and Reproduction

• Nucleic acid
• Either DNA or RNA, but not both
• Helical, closed loop, or a long strand
• Protein coat surrounds nucleic acid (capsid)
• Some have a membrane like structure outside
  capsid called an envelope
• Ex influenza, herpes, chickenpox, HIV

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18.2 Viral Structure and Reproduction

• Bacteriophages virus that infects bacteria.

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18.2 Viral Structure and Reproduction
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Flu Attack

• http//www.youtube.com/watch?vRpj0emEGShQ

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18.2 Viral Structure and Reproduction
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Attachment to a host cell
18.2 Viral Structure and Reproduction

• Virus - recognize and attach to a receptor site
  on the plasma membrane of host
• Protein on capsid locks with receptor site
• Each virus has a specifically shaped attachment
  protein (jigsaw puzzle)
• Can only attach to a few hosts

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Viruses cause two types of infections.
18.2 Viral Structure and Reproduction

1. Lytic
2. Lysogenic

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Lytic cycle
18.2 Viral Structure and Reproduction

• Virus invades a host cell
• ? Produces new viruses (Transcription,
  Translation and Protein Assembly)
• ? Immediately destroys host releasing newly
  formed viruses - Virulent virus
• Lysis - cell disintegration

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Lytic Cycle
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Lysogenic Cycle
18.2 Viral Structure and Reproduction

• Infect a cell without causing its immediate
  destruction - Temperate virus
• Viral DNA is integrated into hosts DNA
  Prophage-Provirus
• Can stay in host cell for an extended period of
  time
• Every time host cell reproduces prophage is
  replicated
• Every cell is also infected
• Trigger will activate lytic cycle later
• Ex Herpes, chicken pox

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Lysogenic Cycle
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Retroviruses
18.2 Viral Structure and Reproduction

• RNA viruses
• Most complex replication cycle
• Ex HIV
• Once inside host retrovirus makes DNA
• Reverse transcriptase produce DNA from viral
  RNA
• Then it is integrated and becomes a prophage
• If reverse transcriptase is in a person then they
  have been infected with a retrovirus

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Common human viral diseases
18.3 Viral Diseases

• Rabies - transmitted by the bite of an infected
  animal
• Virus is carried in saliva
• Virus travels from wound to central nervous
  system
• Fever, headache, throat spasms, paralysis, coma

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Chicken pox
18.3 Viral Diseases

• Virus multiplies in lungs, uses blood vessels to
  reach skin
• Fever, skin rash
• Transmission from direct contact with the skin
  rash and through the air
• Recovery - usually followed by a lifelong
  resistance to re-infection
• Can persist in nerve cells as a prophage - cause
  shingles later in adulthood
• Fever is higher
• Immune system weakens
• Pneumonia may occur

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HIV
18.3 Viral Diseases

• Human immunodeficiency virus
• Infects white blood cells
• Prophage eventually enters lytic cycle leading to
  rapid decrease in white blood cells
• AIDS - acquired immunodeficiency syndrome
• Person dies from other infections

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Prevention and Treatment
18.3 Viral Diseases

• Treatment
• Antiviral Drugs- interfere with viral nucleic
  acid synthesis
• Prevention
• Vaccination - stimulates bodys immune system to
  provide protection against that pathogen
• Inactivated - viruses do not replicate in a host
  system
• Attenuated - viruses are genetically altered so
  that they are incapable of causing disease under
  normal circumstances
• (Preferred - protection is greater and lasts
  longer)

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18.3 Viral Diseases
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18.4 Bacteria and Archaebacteria
KEY CONCEPT Bacteria and Archaeabacteria are
both single-celled prokaryotes.
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Bacteria
18.4 Bacteria and Archaebacteria

• Classification
• Kingdom Monera
• Eubacteria (germs) Archaeabacteria

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Microscopic Prokaryotes
18.4 Bacteria and Archaebacteria

• No nucleus
• No membrane-bound organelles
• Unicellular
• Can do cell functions!
• Alive!

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Archaebacteria The extremists
18.4 Bacteria and Archaebacteria

• Cell wall lacks Peptidoglycan (protein
  carbohydrate compound found in cell walls of
  eubacteria)
• Unusual lipids (fats) in their cell membranes
• Introns (non-coding genes) in their DNA

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Extreme Environments Examples
18.4 Bacteria and Archaeabacteria

• Methanogens
• Convert hydrogen and carbon dioxide into methane
  gas
• Live in anaerobic conditions ex bottom of a
  swamp and sewage, intestinal tract of humans and
  other animals
• Extreme Halophiles
• Live in high salt concentrations
• Use salt to generate ATP

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18.4 Bacteria and Archaeabacteria

• Thermoacidophiles
• Live in extremely acidic environments that have
  extremely high T
• T up to 110 degrees C (230 degrees F)
• Ph less than 2
• Hot springs, volcanic vents, hydrothermal vents

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Eubacteria commonly named for shape
18.4 Bacteria and Archaebacteria

• Bacilli
• Rod-shaped
• Spirilla
• Spiral
• Cocci
• Spherical
• Streptococci
• Chains of cocci
• Staphylococci
• Grapelike clusters of cocci
• Vibrio
• Coma shaped

Cocci spherical
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Eubacteria structure
18.4 Bacteria and Archaebacteria

• Cell membrane - contains enzymes for cellular
  respiration
• DNA is a single, closed loop
• Capsule - outer covering made of polysaccharides
  (sugars) protect it against drying out or harsh
  chemicals
• Pili - short hair-like structures of some species
  
• Help bacteria stick to host cells
• Used to transfer genetic material

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Movement Structures
18.4 Bacteria and Archaebacteria

• Flagella - turn and move the bacterium (single or
  multiple)

• Layer of slime - wavelike contractions of outer
  membrane propel it

• Spiral - shaped bacteria move by corkscrew-like
  rotation

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18.4 Bacteria and Archaebacteria
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Endospores
18.4 Bacteria and Archaebacteria

• Dormant structure that is produced by some
  gram-positive bacteria that are exposed to harsh
  environmental conditions
• Help bacteria resist high temperatures, harsh
  chemicals, radiation, drying and other
  environmental extremes
• If conditions become favorable endospore will
  open, allowing the living bacterium to emerge and
  multiply

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18.4 Bacteria and Archaebacteria

• Gram staining identifies bacteria.

• Stains peptidoglycan
• Gram-negative - stains pink - less peptidoglycan
• Gram-positive - stains purple - more
  peptidoglycan

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Gram-positive bacteria
18.4 Bacteria and Archaebacteria

• Examples
• Streptococci - causes strep throat
• Grow in milk producing lactic acid ? yogurt
• Lactobacilli - found on teeth cause tooth decay
• Actinomycetes - form branching filaments, found
  in soil, and produce
  antibiotics
• Exotoxin - secreted into the environment and
  cause disease

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Gram-Negative Bacteria
18.4 Bacteria and Archaebacteria

• Examples
• Escherichia coli - lives in human intestine where
  it produces vitamin K and assists enzymes in the
  breakdown of foods
• Salmonella - responsible for food poisoning
• Chemoautotrophs
• Endotoxin - Not released until bacteria die

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18.4 Bacteria and Archaebacteria

• Gram positive and gram negative have different
  susceptibilities to
• Antibacterial drugs
• Produce different toxic materials
• React differently to disinfectants

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18.4 Bacteria and Archaebacteria

• Autotroph
• Photoautotrophs - sunlight to make E
  (Cyanobacteria)
• Chemoautotrophs chemicals to make E
• Heterotroph
• Saprophyte - feed on dead and decaying material
• parasitic

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Ex AutotrophCyanobacteria (Blue-Green algae)
18.4 Bacteria and Archaebacteria

• Photosynthetic
• Encased in a jellylike substance and often cling
  together in colonies
• Eutrophication - population bloom - sudden
  increase in the number of an organism due to
  large increase of nutrients

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Eubactria can be grouped by their need for oxygen
18.4 Bacteria and Archaebacteria

• Obligate anaerobes - are poisoned by oxygen
• Obligate aerobes - need oxygen
• Facultative aerobes - live with or without oxygen

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18.4 Bacteria and Archaeabacteria

• Examples
• Obligate Anaerobes - Clostridium tetani
• Facultative aerobes - E. coli
• Obligate Aerobes - Mycobacterium tuberculosis

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Asexual Reproduction
18.4 Bacteria and Archaebacteria

• Binary Fission
• Rapid

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Genetic Recombination
18.5 Beneficial Roles of Prokaryotes
18.4 Bacteria and Archaebacteria

• Transformation - bacterial cell takes in DNA from
  external environment
• Conjugation - two bacteria bind together
• One transfers genetic information to the other
• Pili binds to bacteria to form a conjugation
  bridge

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18.4 Bacteria and Archaebacteria
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Provide nutrients to humans and other animals.
18.5 Beneficial Roles of Prokaryotes

• Live in digestive systems of animals.
• Make vitamins
• Break down food

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18.5 Beneficial Roles of Prokaryotes

• Ferment many foods

• Yogurt, cheese

• Pickles, sauerkraut
• Soy sauce, vinegar

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Play important roles in ecosystems.
18.5 Beneficial Roles of Prokaryotes

• Photosynthesize
• Recycle carbon, nitrogen, hydrogen, sulfur
• Fix nitrogen

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18.5 Beneficial Roles of Prokaryotes

• Bioremediation uses bacteria to break down
  pollutants.

• Oil spills

• Biodegradable materials

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18.6 Bacterial Diseases and Antibiotics
KEY CONCEPT Understanding bacteria is necessary
to prevent and treat disease.
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Bacteria cause disease
18.6 Bacterial Diseases and Antibiotics

• Plants and animals
• Carried in air, food, and water
• Growth of bacteria can interfere with normal
  function of body
• Or it can release a toxin that directly attacks
  host

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Bacterial Diseases
18.6 Bacterial Diseases and Antibiotics
18.5 Beneficial Roles of Prokaryotes

• Transmitted by ticks
• Borrelia burgdorferi - causes Lyme disease
• Bulls eye rash around bite mark
• Sever headaches, backaches, chills, and fatigue -
  can lead to death
• Rickettsia rickettsii - causes Rocky Mountain
  spotted fever
• 3-12 days after infection - high fever and severe
  headache
• 3-5 days after that - rash on extremities,
  diarrhea, cramps - can lead to death

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18.6 Bacterial Diseases and Antibiotics

• Normally harmless bacteria can become destructive

• May colonize new tissues

• Immune system may be lowered

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Antibiotics - interfere with bacteria cellular
functions
18.6 Bacterial Diseases and Antibiotics
18.5 Beneficial Roles of Prokaryotes

• Penicillin - interferes with cell wall synthesis
• Tetracycline - interferes with protein synthesis
• Sulfa Drugs - are made in laboratories

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Bacteria can evolve resistance to antibiotics.
18.6 Bacterial Diseases and Antibiotics

• Overuse
• Underuse
• Misuse

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Antibiotic Resistance
18.6 Bacterial Diseases and Antibiotics
18.5 Beneficial Roles of Prokaryotes

• Population of bacteria are exposed to antibiotic
• Most susceptible bacteria die first
• A few mutant bacteria are resistant and continue
  to grow and multiply
• Results in a resistant population

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Why Antibacterial Soap is Dangerous!
18.6 Bacterial Diseases and Antibiotics

• http//www.youtube.com/watch?vkXt0I48LveEfeature
  em-subs_digestlistTLZh8awZSvbJA

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How we conquered the deadly smallpox virus -
Simona Zompi

• http//www.youtube.com/watch?vyqUFy-t4MlQ