Microbiology and viruses

• Microbiology


  The study of microscopic organisms (ie. organisms not visible to the naked eye)
• Microscopic organisms


  • Viruses
  • Bacteria (Archaea & eubacteria)
  • Protists (paramecium)
  • Some fungi (yeast)
• Viruses


  Non-cellular particles made up of genetic material and protein that can invade living cells
• Viruses can infect all types of life forms, from animals and plants to microorganisms, including eubacteria and archaea
• Structure of viruses


  • Lack cellular structures such as cell membrane, membrane-bound organelles (nucleus, mitochondria, Golgi apparatus)
  • Lack cellular activity to reproduce without the help of a host cell
  • Completely inert and inactive unless they have taken over a host cell
• Components of virus structure

  • Capsid (protein coat which provides protection for the genetic material)
  • DNA/RNA (genetic material which provides instruction to the host cell on how to make new viruses)
  • Enzymes (aid viral entry and/or take over of the host cell)
  • Specific receptors (allow the virus to gain entry to a specific host cell)
• Bacteriophages (viruses that infect bacteria)


  • Have tail fibres which serve as receptors for attaching to the specific host cell
• Lytic Cycle

  1. Attachment

  2. Phage assembly

  3. Release

  4. Entry of phage DNA and degradation of host DNA

  5. Synthesis of viral genomes and proteins
• Lytic Cycle

  • The viral life cycle which involves take over of the host cell
• Virulence


  • The ability of a virus to complete the lytic cycle
  • The more virulent the virus, the more infectious it is
• Lysogenic Cycle


  1. Attachment

  2. Penetration

  3. Integration

  4. Replication
• Prophage

  The viral genetic material that gets inserted into the host cell's genetic material
• During the lysogenic cycle, the host cell remains unaltered externally
• The viral genetic material does not immediately take over the host cell, therefore new viruses are not produced
• When the host cell replicates its DNA, the viral DNA gets copied along with it
• After several cell cycles, numerous daughter cells with the integrated prophage will be created
• The prophage may later be activated, perhaps due to a viral infection, at which time the virus could start the lytic cycle
• Bacteria

  Prokaryotes lacking a nucleus and other membrane-bound organelles
• Bacteria

  • Have a circular chromosome of double-stranded DNA
  • Average bacteria is about 1μm long (0.001m)
• Bacterial shapes

  • Spherical (Cocci)
  • Rod-shaped (Bacilli)
  • Helical (Spirilli)
• Bacterial clusters and chains

  • Clusters have the prefix Staphylo- (e.g. Staphylococcus)
  • Chains have the prefix Strepto- (e.g. Streptobacillus, Streptobacillus)
• Bacterial habitats

  • Oceans
  • Freshwater
  • Soil
  • On/in other organisms
  • Harsh environments (e.g. Arctic, salt marshes, deep-sea vents, hot springs)
• Bacteria are the foundation upon which ecosystems like hydrothermal vent ecosystems are built
• Archaea

  Prokaryotes that are dramatically different from other bacteria and live in harsh habitats
• Types of Archaea

  • Methanogens
  • Extreme halophiles
  • Extreme thermophiles
• Methanogens

  Produce methane from carbon dioxide, live in swamps, marshes, and animal guts
• Extreme halophiles

  Thrive in environments 10 times saltier than seawater, like the Great Salt Lake and Dead Sea
• Extreme thermophiles

  Require high temperatures to grow, found near hydrothermal vents in waters exceeding 100°C
• Eubacteria tend to be found in less extreme environments than Archaebacteria
• Prokaryotic cells lack organelles such as mitochondria or chloroplasts found in eukaryotes.
• Two Types of Bacteria

  Archaebacteria -live in harsh habitats, are dramatically different than other bacteria

  Eubacteria - “normal” bacteria
• Chemotrophs


  Use the energy of chemical reactions to produce food
• Ways chemotrophs obtain energy

  • 5 ways
• Aerobes


  • Must have oxygen to survive
• Bacteria need a constant supply of energy to perform life activities
• Ways bacteria obtain energy

  • 3
• Obligate aerobes


  • Must have oxygen to survive and grow
• Obligate anaerobes


  • Can only grow and obtain energy in the absence of oxygen
• Faculative anaerobes


  • Can survive, grow and obtain energy with or without oxygen
• Attachment


  The process by which a phage attaches to the host cell's surface receptors, allowing the phage to inject its DNA into the host cell.