MICROORGANISMS

• Microorganisms


  Extremely tiny organisms that can only be seen using a microscope, including bacteria, archaea, fungi, algae, protozoans and viruses
• Microorganisms


  • Bacteria
  • Archaea
  • Fungi
  • Algae
  • Protozoans
  • Viruses
• Prokaryotic cell


  • Simple cell structure with no nucleus or membrane bound organelles
• Eukaryotic cell


  • Complex cell structure with nucleus and specialized organelles
• Microbes account for most of the diversity of life on our planet
• Domains of microorganisms


  • Eubacteria (true bacteria)
  • Archaebacteria (primitive bacteria)
  • Eukarya (organisms with eukaryotic cell structure)
• Eubacteria (true bacteria)


  • Microscopic, unicellular, may occur singly or in colonies
  • Possess rigid cell wall made of peptidoglycan and lipopolysaccharides
  • Lack well-defined nucleus, DNA not enclosed in nuclear membrane
  • Ribosomes scattered in cytoplasmic matrix, 70s type
  • Most are autotrophic, some are heterotrophic
  • Motile bacteria possess flagella
• Bacterial morphology


  • Coccus (spherical, round or ovoid)
  • Bacillus (rod-shaped)
  • Spirillum (spiral-shaped)
• Archaea


  • Prokaryotic with single cell organization
  • Lack peptidoglycan in cell walls
  • Thrive in extreme environments
• Archaea groups


  • Methanogens
  • Extreme halophiles
  • Extreme thermophiles
• Eukarya


  • Organisms with cells containing nucleus and membrane-bound organelles
• Microorganisms in Eukarya domain

  • Fungi
  • Protists
• Fungi


  • Filamentous multicellular hyphae like moulds and mushrooms, or non-filamentous unicellular yeasts
  • Mostly decomposers utilizing dead organic matter, some are parasites of plants and animals
  • Grow best in moist environments
• Protists


  • Algae
  • Slime moulds
  • Water moulds
  • Protozoans
• Algae


  • Plant-like protists, autotrophic and capable of photosynthesis, primary producers in aquatic environments
• Slime moulds


  • Saprophytic protists, single-celled organisms living in moist soil and decaying plants/trees, form multicellular aggregations called plasmodium
• Water moulds


  • Found in wet environments, have filamentous hyphae and feed on decaying tissue like rotting logs and mulch
• Protozoan groups


  • Mastigophora (use flagella)
  • Sarcodina (use pseudopodia)
  • Ciliophora (use cilia)
  • Sporozoans (form spores)
• Viruses, viroids and prions

  Acellular entities, not considered living beings when not on their host, but can cause diseases
• Most microbes are either beneficial or harmless to humans, less than 1% are pathogenic
• Diseases caused by pathogens

  • African Trypanosomiasis (sleeping sickness)
  • Cholera
  • Dengue
  • Hepatitis
  • Pneumonia
  • Rotavirus
  • Schistosomiasis
  • Tuberculosis
  • AIDS
• Beneficial microorganisms


  • Involved in photosynthesis, decomposition, nitrogen fixation, food/beverage production, medical advances, and improving digestion