Classifications of Micro-organism

• Viruses are acellular organisms that do not have organelles, nucleus, or cytoplasm, and cannot carry out the seven basic life functions
• Viruses


  • They have a capsid (protein coat) that protects the internal structures
  • Some have an envelope (additional protective layer)
  • They contain either DNA or RNA as their genetic material
• Viruses


  • Influenza virus
  • Bacteriophage
• Bacteriophage reproduction


  1. Attaches to bacterial cell

  2. Injects DNA through neck and tail

  3. DNA replicates inside bacterial cell
• Viruses can cause many fatal diseases
• Bacteria


  • They are unicellular (single-celled) or exist in colonies
  • They have three main shapes: cocci (circular), bacilli (rod-shaped), and vibrios (curved rods)
• Bacterial cell structure


  • Capsule (protective outer layer)
  • Cell wall (for rigidity and protection)
  • Cell membrane (plasma membrane)
  • Cytoplasm (with freely floating DNA/nucleoid)
  • Ribosomes
  • Plasmids (for faster replication and adaptation)
  • Flagella (for movement)
  • Pili (for attachment to host)
• Bacteria are prokaryotes, unlike eukaryotic cells they lack membrane-bound organelles
• Protists


  • They can be unicellular or multicellular
  • They share characteristics with both prokaryotes and eukaryotes
• Protists have a nucleus and other membrane-bound organelles, unlike bacteria
• Unicellular


  One cell, living on their own often in a body of water
• Multicellular


  Many cells making up one organism, e.g. seaweed
• Protists


  • Have a nucleus and membrane-bound organelles
  • Many are photosynthetic and make up the majority of ocean plankton
• Contractile vacuole


  Unique to protists, regulates water absorption to prevent drowning
• Flagellum


  Tail-like structure for movement, found in both protists and bacteria
• Food vacuole


  Where protists store and digest food
• Pseudopodia


  False feet used by protists to surround and digest food
• Fungi


  • Cannot photosynthesize, absorb nutrients from dead or dying matter
  • Can be unicellular or multicellular
• Hyphae


  Long, interconnected fungal cells that lack cell walls between them
• Rhizoids


  Root-like structures used by fungi to absorb nutrients
• Stolon


  Horizontal hyphae growing above the substrate
• Mycelium


  The entire body of a fungus, including hyphae, rhizoids and stolons
• Sporangiophore


  Structure that produces spores for fungal reproduction
• Sporangium


  The spore-containing structure at the end of a sporangiophore
• Terminology recap


  • Prokaryotes
  • Eukaryotes
  • Viruses
  • Capsid
  • Envelope
  • Pathogenic
  • Bacteria
  • Coccus
  • Bacillus
  • Spirillum
  • Flagella
  • Pili
  • Plasmid
  • Protists
  • Contractile vacuole
  • Food vacuole
  • Pseudopodia
  • Fungi
  • Saprophytic
  • Hyphae
  • Rhizoids
  • Stolon
  • Mycelium
  • Sporangiophore
  • Sporangium
  • Spores