Bacteria and Viruses

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Bacteria and Viruses

• Friends or Foes?

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A. Bacteria

• All prokaryotes were originally placed in the
  kingdom Monera, but the kingdom has since been
  separated into two distinct domains (Bacteria and
  Archae)
• Types of bacteria
• Eubacteria - common bacteria
• Cyanobacteria - photosynthetic bacteria
• Archaebacteria - live in extremely harsh
  environments (Examples - halophiles,
  thermophiles, methanogens)

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A. Bacteria

• Three basic shapes
• Bacillus - rod
• Coccus - round
• Spirillum - spiral
• Cell arrangement
• Di - two cells
• Strepto - long chains
• Staphylo - clusters
• Cell walls
• Some have one thin layer of carbohydrates and
  protein (peptidoglycan)
• Others have this thin layer plus a second outer
  layer of lipids and carbohydrates

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A. Bacteria

• Movement
• Cilia - short, hair-like projections
• Flagellum - long, whip-like tail
• Obtaining energy
• Autotrophs
• Phototrophic - sunlight
• Chemotrophic - obtain energy from inorganic
  molecules such as ammonia and sulfur
• Heterotrophs
• Chemotrophic - obtain energy from organic
  molecules
• Phototrophic - photosynthetic and heterotrophic

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A. Bacteria

• Respiration
• Obligate aerobes - need oxygen
• Obligate anaerobes - no oxygen
• Facultative anaerobes - with or without oxygen

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A. Bacteria

• 9. Reproduction
• Binary fission
• Asexual form of reproduction
• Cell division
• Conjugation
• Genetic information from one cell transferred to
  another cell
• Increases genetic diversity
• Spores
• Formed by some bacteria when conditions do not
  support growth
• Allow survival in harsh conditions

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A. Bacteria

• 10. Role of bacteria in the environment
• Beneficial
• Decomposers recycle nutrients (saprophytes)
• Nitrogen fixation - bacteria in the soil take in
  atmospheric nitrogen and convert to useable forms
  for plants
• Bioremediation - example sewage decomposition
• Used to produce food and drugs
• Biotechnology - used in cloning genes, production
  of insulin
• Symbiosis - two organisms in a close relationship
• Harmful
• Pathogens - disease-causing agents
• Examples Tuberculosis, Bubonic plague,
  Tetanus, Lyme disease
• Cause tooth decay
• Food contamination
• Biological weapons

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A. Bacteria

• 11. Controlling bacteria
• Sterilization
• Vaccines - small, harmless dose of a pathogen to
  induce an immune response
• Antibiotics - antibacterial drugs
• What happens when the antibiotics no longer
  work?

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B. Viruses

• Virus - noncellular particle composed of genetic
  material and protein, capable of invading living
  cells
• Structure
• Basic structure core of nucleic acid (DNA or
  RNA) surrounded by a protein coat (capsid)
• Shapes rod, tadpole, helical, cubelike
• Size 20 to 400 nm
• Example Bacteriophage T4 is composed of a core
  of DNA within a capsid with a protein tail

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B. Viruses

• Viral life cycles
• Lytic viruses
• Virus attaches to host cell and injects DNA
• Cell replicates, transcribes, and translates
  viral DNA and RNA
• Production of more viral DNA and proteins results
  in more viruses
• Cell lyses releases new viruses
• Lysogenic viruses have a similar life cycle, but
  their DNA remains dormant in host DNA until an
  environmental change results in the release of
  the viral DNA (prophage) and the beginning of a
  lytic cycle
• Retroviruses contain RNA
• RNA must first be reversely transcribed into DNA
• Reverse transcriptase - enzyme that copies DNA
  from RNA
• Example HIV

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B. Viruses

• Viral diseases
• Examples Chicken pox, rabies, common cold,
  polio, the flu
• Vaccines may work against some viruses, but not
  all
• Some viruses have surface proteins that do not
  change and, therefore, are easy to target
• Other viruses (such as HIV and influenze) have
  surface proteins that mutate frequently