Bacteria and Viruses

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Chapter 19

• Bacteria and Viruses

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I. Prokaryotes

• Prokaryotes single-celled organisms that lack a
  nucleus
• 1. Eubacteria walls contain
  peptidoglycan (a carbohydrate)
• 2. Archaebacteria lack peptidoglycan, DNA
  similar to eukarotes

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• Identifying Prokaryotes
• 1. Shapes
• a. Bacilli (rod shaped)
• b. Cocci (spherical)
• c. Spirilla (spiral)

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• 2. Cell Walls
• a. Gram-positive (w/peptidoglycan)
  purple
• b. Gram-negative (w/o peptidoglycan
  red

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3. Arrangement

• Staphyl Clumps or clusters
• b. Strepto long chains

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4. Movement

• Propelled by tail-like structure called flagella
• b. Glide along a slime secretion
• c. Move along like snakes
• d. Some dont move

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• Obtaining Energy
• 1. Autotrophs
• a. Photoautotrophs obtain energy from
  photosynthesis
• b. Chemoautotrophs obtain energy from
  inorganic molecules

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• 2. Heterotrophs
• a. Can cause food poisoning
• b. Photoheterotrophs photosynthetic,
  but also need organic compounds for
  nutrition

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• Releasing Energy
• 1. Obligate aerobes require oxygen
• 2. Obligate anaerobes cannot live in
  presence of oxygen
• 3. Facultative anaerobes do not need
  oxygen, but can live in the presence of it

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• Growth and Reproduction
• 1. Binary fission cell divides, asexual
• 2. Conjugation transfer of genetic
  information from one cell to another, sexual
• 3. In unfavorable conditions, many
  bacteria can form endospores can remain
  dormant for months or years

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II. Bacteria in Nature

• Decomposers
• 1. Help recycle nutrients break down dead
  organisms
• 2. Used in sewage treatment

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• Nitrogen Fixers
• 1. Nitrogen fixation converting nitrogen
  into a form plants can use
• 2. Rhizobium grow on roots of
  soybeans and other legumes converts
  nitrogen to ammonia for the plant

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• Bacteria and Disease
• 1. Pathogen disease-causing agents
• 2. 2 ways bacteria cause disease
• a. Break down tissues for food
• b. Release toxins
• 3. Many can be prevented with vaccines,
  can be treated with antibiotics

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• Human Uses of Bacteria
• 1. Food cheese, yogurt, buttermilk, sour
  cream, pickles, sauerkraut
• 2. Industry cleaning up oil spills,
  mining minerals, synthesizing drugs

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• 3. Bacteria live in our digestive tract to help
  in digestion (called normal flora)

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• Controlling Bacteria
• 1. Sterilization destroy bacteria by
  subjecting them to great heat or chemicals
• a. Boiling, frying, steaming can all
  kill bacteria
• b. Disinfectant chemical solutions can
  be used in homes and hospitals
• 2. Refrigeration bacteria grow slowly at
  low temperatures

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III. Viruses

• Viruses particles of nucleic acid and protein
• 1. Nucleic acid DNA or RNA that
  contains instructions for making new copies of
  the virus
• 2. Capsid outer protein coat

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• Viral Infection
• 1. Infect cells and replicate inside host
  cell
• 2. Bacteriophage viruses that infect
  bacteria

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• 3. 2 types of viral infections
• a. Lytic infection virus enters cell,
  make copies of itself and causes the cell
  to burst
• b. Lysogenic infection virus embeds its
  DNA into DNA of host and is replicated
  with host cells DNA

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• Viruses and Disease
• 1. Many viruses can be prevented through
  the use of vaccines (polio,
• measles, influenza)
• 2. Oncogenic viruses cause cancer
• 3. Retroviruses contain RNA
• 4. Prions contain no DNA or RNA, only protein