Animal and plant pathogens

• What is a pathogen?

  Microorganisms that cause disease
• What are examples of pathogens?

  • Bacteria
  • fungi
  • protoctista
  • Virus
• What is a vector?

  A living or non living factor that transmits a pathogen from one organism to another
• What kingdom do bacteria belong to?

  Prokaryotae
• State the different shapes of bacteria

  • Bacillus (rod)
  • coccus (spherical)
  • vibrio (comma)
  • spirillum (spiral)
  • spirochaete (corkscrew)
• How do gram positive and negative bacteria cell walls stain in response to gram staining? How is it useful?

  
  

  • Gram positive - purple blue under light microscope (MRSA)
  • Gram negative - red under light microscope (E coli, gut bacteria)

  type of cell wall affects how bacteria react to different antibiotics
• What are viruses? How do they infect a host?

  • Non living infectious agents
  • genetic material surrounded by protein
  • reproduces rapidly, evolve by developing adaptations to host
  • genetic material of the virus takes over the biochemistry (DNA) of the host to make more viruses
• Name a virus that attacks bacteria and describe what it does

  • Bacteriophage
  • take over bacteria and uses its DNA to replicate, destroying bacteria at same time
  • then its infects other bacteria cells
• What is a communicable disease?

  A disease that can be transmitted from one organism to another, of the same or different species
• What two main ways can bacteria be classified as?

  • Their shape (rod, comma, spiral, etc)
  • Their cell walls (gram positive or negative)
• Describe a protist

  • Small percentage are Pathogenic- spreads communicable diseases to plants and animals
  • Parasitic- use people or animals as host organisms
  • May need vector to be transmitted
  • Eukaryotic
  • Variety of feeding mechanisms
• Describe fungi

  • Eukaryotic
  • Can’t photosynthesise so digest food extracellularly before absorbing nutrients
  • Saprophytes- feed on dead matter
  • Some are parasitic- feed on living plants and animals- these are the pathogenic fungi which cause disease
  • Produce millions of spores
  • Affect plants- starvation
• How do viruses damage host tissue?

  • Take over cell metabolism
  • Viral genetic material inserted into host DNA
  • Virus uses the host cell to make new viruses- viral nucleus acid replicates
  • these burst out of the cell, (lysis) destroying it and then spreading to infect other cells
• how do protists damage host tissue?

  • don’t take over genetic material
  • digest and use cell contents as they reproduce
• how do fungi damage host tissues?

  • digest living cells and destroy them
  • some can produce toxins which cause disease
• how do bacteria damage host tissues?

  • produce toxins
  • poison or damage host cell
  • breaks down cell membranes
  • damage or inactivation of enzymes
  • interference with the host genetic material so cells can’t divide
  • Toxins are by product of normal bacterial functioning
• how do viruses enter cells? (PPQ)

  • Through damage/wound in the cell
  • or carried by insects/vectors/aphids