Identifying and Classifying Bacteria

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Identifying and Classifying Bacteria

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What is a prokaryote?

• Cells that lack a true nucleus.
• Cells that lack membrane-bound organelles.
• Most surrounded by a cell wall.
• Many secrete a protective slime capsule.

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How big is a prokaryotic cell?

• 1- 5 micrometers
• (1 millionth of a meter)

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Classification

• Archae vs Bacteria

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Archae

• Surrounded by a cell wall lacking peptidoglycan.
• Live in extreme conditions

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Examples of Archae

• Methanogens convert H2 and CO2 into methane gas
  for energy
• Halophiles love salt
• Thermoacidophiles love heat and acid

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Bacteria

• Surrounded by a cell wall made of peptidoglycan.
• Example E. coli

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Identifying Prokaryotes

• 1. Shape
• Coccus spherical
• Bacillus rod-shaped
• Spirillum spiral
• Vibrio comma shape

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Bacillus
Coccus
Vibrio
Spirillum
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Cocci and Bacilli may group together
Prefixes for arrangements Diplo two
Ex. Diplococcus
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Strepto chain
Streptococcus
Streptobacillus
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Staphylo - clustered
Staphylococcus
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2. Motility ability to move

• Flagella whip-like structure used to propel
  bacteria
• Slime glide along slime secretion
• Spiral motion cork-screw motion (spirillum)

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3. Metabolism Oxygen or NOT

• Obligate Aerobes Need oxygen
• Obligate Anaerobes cannot live in oxygen
• Facultative anaerobes can live with or without
  oxygen

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3.Metabolism Obtaining Energy

• Autotroph vs. Heterotroph
• Photoautotroph- uses light energy for
  photosynthesis
• Chemoautotroph- uses energy from inorganic
  chemicals for chemosynthesis

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• Photoheterotrophs- uses photosynthesis and eats
  organic compounds
• Heterotroph consumes organic compounds

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Bacterial Reproduction
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Asexual Binary fission

1. Circular DNA replicates
2. Cell membrane and cell wall divide
3. Identical daughter cells separate

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How fast does this happen?

• http//www.youtube.com/watch?vgEwzDydciWcfeature
  related
• approximately every 20 minutes

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Disease

• Pathology is the study of disease.
• Pathogens organisms that cause disease.

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Gram-staining Test

• Gram-positive bacteria contain lots of
  peptidoglycan in cell walls. Stains purple.
• Gram- negative bacteria contain little
  peptidoglycan in cell walls. Stains red.

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Exotoxins

• Poisonous proteins that are released by some
  gram-positive bacteria.

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For example

• Clostridium tetani secretes an exotoxin that
  causes tetanus.
• Tetanus causes stiffness in muscles.
• Clostridium botulinum produces a very powerful
  exotoxin that causes the fatal disease, botulism.
• 1 g of botulism toxin can kill 1 million people.

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Endotoxins

• Lipids and carbohydrates in the cell membranes of
  some Gram-negative bacteria, that are poisonous.
• They are released when the bacteria die.

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For example

• Most species of Salmonella, are endotoxin
  producing bacteria.
• Salmonella typhi, causes typhoid fever.

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Antibiotics

• Antibiotics interfere with the bacterias
  cellular activities.

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For example

• Penicillin blocks the building of the cell wall.
• Accidently discovered by Alexander Fleming in
  1920s
• Tetracyline blocks protein synthesis.

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Where do antibiotics come from?

• Antibiotics are naturally made by some fungi and
  bacteria.
• Some are made synthetically in labs.

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Antibiotic-Resistance

• Bacteria can quickly adapt to their environment
  because of their rapid rate of reproduction.

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Antibiotic-Resistance

1. If one bacterium mutates and becomes resistant,
2. then in the presence of antibiotics, bacteria not
   resistant die
3. Those with the resistance take over the
   population.