Types of Pathogen

• Bacteria


  • Are prokaryotes (no membrane bound organelles or nucleus)
  • Some are non-pathogenic
• Virus


  • Are non-living infectious agents
  • Have a diameter of 0.02 to 0.03 micrometres
  • Genetic material (RNA or DNA) is surrounded by protein
  • No cellular structure - cannot respire, produce ATP, repilcate genetic material
• Protoctista (Protista)


  Are eukaryotic organisms

  Can be single-celled or grouped in colonies

  May use a vector
• Fungi


  Eukaryotic organisms

  Can be multicellular or single-celled

  Cannot photosynthesise

  Digest food extracellularly

  Can be saprophytes (feed on dead or decaying matter) or parasitic (feed on living plants/animals)

  Bodies consist of filaments called hyphae - form a network and spread throughout host/soil
• How viruses work?


  They invade living cells and the genetic material of the virus takes over the biochemistry of the host cell to make more of the pathogen
• How do fungal infections work?

  They infect the leaves of the plant, preventing them from photosynthesising killing the plant
• Example of a bacterial infection

  Ring rot - infects vascular tissue and prevent the transport of water, affects potatoes, tomatoes and aubergines damaging the leaves, tubers and fruit of the plant
• Example of a bacterial infection

  Tuberculosis (TB) - infects the lungs causing a chronic cough and bloody mucus, affects humans, cows, pigs, badgers and deer
• Example of a bacterial infection

  Meningitis - infection of the meninges of the brain
• Example of a virus

  Tobacco Mosaic Virus (TMV) - infects Tobacco plant and around 150 other plant species like tomatoes and peppers. Causes damage to the leaves, flowers or fruit of the plant. There is no cure but there are resistant crop strains
• Example of a virus

  HIV/AIDS - acquired immunodeficiency syndrome caused by HIV which targets T-helper cells that slowly destroys the immune system
• Example of a virus

  Influenza - an infection of the ciliated epithelial cells, killing them and leaving the airways open to a secondary infection like pneumonia
• Example of a protoctista (protista)


  Potato blight - penetrates the host cell, destroying the leaves, tubers and fruit on the plant. There is no cure but there are resistant strains
• Example of a protoctista (protista)


  Malaria - caused by Plasmodium and is spread by the bites from Anopheles mosquitoes
• Examples of fungi


  Black sigatoka - spreads through leaves and reduces ability to photosynthesise, there is no cure but there are preventative measures e.g. fungicides
• Examples of fungi


  Ringworm - pathogen affects mammals like cattle, dogs, humans and cats. Different fungi infect different species. Antifungal creams are a potential cure
• Examples of fungi


  • Athlete's foot - is a human disease/form of human ring worm that grows on the skin between the toes. A cure is antifungal creams