Prokaryotes and Viruses

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Prokaryotes and Viruses

• Biology I

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16.1 Prokaryotic life began on a young Earth

• Stromatolites Ancient fossils found in
  dome-shaped rocks
• Used as evidence bacteria were present 3.5
  billion years ago.

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How did life begin?

• Origin of small molecules
• 1953 Stanley Miller, simulated conditions on
  early Earth
• Formation of Organic Polymers
• How did polymers form?
• Heat and clay help bind organic monomers together
• Lightening was energy source

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Formation Cont.

• What was the original process of inheritance?
• RNA, short strands could replicate without the
  use of enzymes
• Formation of Pre-Cells
• Early organic materials and RNA became encased in
  membranes

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Supports 4 stage process

• First, small organic molecules, such as amino
  acids and nucleotides
• Second, these small molecules joined together
  into larger ones such as proteins and nucleic
  acids.
• Third, molecules that could copy themselves
  provided a basis for the inheritance of molecular
  information.
• In the last stage, these various organic
  molecules became packaged within membranes and
  separated from their surroundings. In other
  words, they formed pre-cells.

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Where did life begin?

• Shallow waters and moist sediments such as clay
• Deep-sea thermal vents

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16.2 Diverse prokaryotes populate the biosphere
Diversity of Prokaryotic Life -found EVERYWHERE
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Archaea

• ancient bacteria
• Extremophiles
• Consists of three types
• Thermophiles heat lovers
• Halophiles salt lovers
• Methogens live anaerobic environment, produce
  methane gas
• DNA evidence indicates closer relationship to
  eukaryotes than bacteria

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Differences between Archaea and Bacteria

• Differences in RNA and DNA information
• Enzymes that catalyze RNA are different
• Bacteria lack introns
• Antibiotics effective only to Bacteria
• Archea cell walls lack petidoglycan

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Structure and Function of Bacteria

• Bacteria is identified and distinguished based
  partly on three characteristics.
• Cell Shape
• cocci (round)
• bacilli(rod)
• spiral(spirochetes)

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Structure and Function of Bacteria

• Cell Wall Structure
• Two types of cell walls
• Determined by a Gram stain
• Gram positive bacterium (purple)
• Gram negative bacterium (pink)

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Structure and Function of Bacteria

• Motility
• Flagella
• Pili
• Slimy threads

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Asexual Reproduction

• Binary fission
• Rapid reproduction
• Cloning of the parent
• Can have mutations, antibiotic resistance

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Sexual Reproduction

• Transformation bacterium takes up free DNA from
  the environment
• Conjugation two bacterial cells temporarily
  join and directly transfer genetic material
  between them
• Transduction virus phage inserts genetic
  material
• Endospore Formation dormant bacteria with
  highly resistant outer wall

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Genetic Variation
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Modes of Nutrition
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Cyanobacteria and Oxygen

• Believe to be the first photoautotrophs.
• Helped bring oxygen in the atmosphere
• Revolutionized the evolution of aerobic organisms
  and cellular respiration.

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16.3 Prokaryotes perform essential functions in
the biosphere

• Chemical recycling help in breaking down or
  decomposing, organic waste products and dead
  organisms
• e.g. carbon locked in organic compounds returned
  to atmosphere as CO2
• Used in nitrogen gas conversion through legumes

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Nitrogen Cycle
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Human uses of bacteria

• Use of organisms to remove pollutants from water,
  air and soil bioremediation
• Used in sewage treatment, oil clean up, mining
  clean up, genetic exploration

PCB clean up
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16.4 Some Prokaryotes cause disease

• Pathogen bacteria or other microorganism that
  cause a disease.
• Bacteria can invade the cell and destroy it
• Develop toxins
• Secrete toxins from the bacterial cell Exotoxins
• can destroy the cell or interfere with cell
  function
• Cause digestive problems or paralysis
• Toxin is a component of the bacterial cell wall
  Endotoxins
• Causes the body to respond (immune system) with
  fever, aches, weakness, or can lead to shock.

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Diseases and Methods of Transmission

• Inhalation
• Anthrax
• Tuberculosis
• Sexual
• Syphilis
• Gonorrhea
• Bites
• Lyme disease
• Improperly stored or prepared foods
• Botulism
• salmonella

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Bacterial Diseases

• Tuberculosis
• Invades tissues and destroys cell
• Engulfs white blood cells

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Bacterial Diseases caused by poisons

• Closstridium botulinum botulism
• 1 gram of pure toxin could kill 1 million people
• Staphylococcus aureus Staph infection
• Secretes a poison by the bacterial cells
• Proteins secreted cause the illness

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Diseases caused by bacteria

• Salmonella
• Is a component of the cell wall that causes the
  illness
• Can also cause typhoid fever

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Defense against bacteria

• Hygiene wash your hands, stay clean
• Clean drinking water
• Dont get run down, weakens the immune system
• Antibiotics, resistance to antibiotics

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16.5 Viruses infect cells by inserting genes

• Virus is not a cell, cannot reproduce on its own.
• Structure of a virus
• Protein coat
• Genetic material, either RNA or DNA

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Virus reproduction

• Two reproductive cycles
• Lytic cycle
• 1. Host cell produce virus parts
• 2. Virus parts assemble
• 3. Host cell bursts, releasing hundreds of
  complete, functioning viruses
• Lysogenic cycle
• 1. Viral DNA combines with host DNA
• 2. Host cell replicates as normal
• 3. Then converts to lytic cycle

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Viral reproduction
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Viruses and Disease

• Viruses have an outer envelop that help the virus
  enter and leave a cell
• Contain RNA as genetic material
• Common cold, flu, measles, mumps, polio, AIDS
• Contain DNA as genetic material
• Hepatitis, herpes infections
• Antibiotic do not work against viruses

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HIV A retrovirus

• Retrovirus uses RNA as genetic material versus
  DNA

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Defense against Viruses

• Vaccines dead or disabled pieces of virus that
  fool immune system, form future resistance
• First vaccine Edward Jenner, small pox vaccine
• Some may not work as the virus mutate too quickly
  for a vaccine to work (HIV)