prokaryotic organisms

• Bacteria


  Microscopic single-celled organisms
• Pathogen

  Microorganisms that can cause disease, including fungi, bacteria, protoctists or viruses
• Bacteria


  • Have a cell wall (not made of cellulose), cell membrane, cytoplasm and plasmids
  • Lack a nucleus but contain a circular chromosome of DNA
  • Lack mitochondria and other membrane-bound organelles found in eukaryotic cells
• Viruses


  • Not living organisms
  • Small particles, smaller than bacteria
  • Parasitic and can only reproduce inside living cells
  • Infect every type of living organism
  • Wide variety of shapes and sizes
  • No cellular structure but have a protein coat and contain one type of nucleic acid, either DNA or RNA
• Bacteria


  • Lactobacillus (a rod-shaped bacterium used in the production of yoghurt from milk)
  • Pneumococcus (a spherical bacterium that acts as the pathogen causing pneumonia)
• Viruses


  • Tobacco mosaic virus that causes discolouring of the leaves of tobacco plants by preventing the formation of chloroplasts
  • Influenza virus that causes 'flu'
  • HIV virus that causes AIDS
• Bacteria feed


  1. Some can carry out photosynthesis despite having no chloroplasts (they possess chlorophyl and enzymes necessary to synthesize sugars from carbon dioxide)

  2. Most feed on other living or dead organisms (if they feed on dead organic matter then they are known as saprobionts or decomposers)