Types of Bacteria

All bacteria share features common to every prokaryotic cell:

  • They lack a nucleus and membrane-bound organelles
  • They have circular DNA that is naked (not bound to protein)
  • They have smaller ribosomes (70S)

However different types of bacteria can be distinguished according to a number of characteristics:

  • Shape – Round (coccus), rod-like (bacillus), comma-shaped (vibrio) or spiral (spirilla / spirochete)
  • Cell wall composition – Gram-positive (thick peptidoglycan layer) or Gram-negative (lipopolysaccharide layer)
  • Gaseous requirements – Anaerobic (obligate or facultative) or aerobic
  • Nutritional patterns – Autotrophic (photosynthetic or chemosynthetic) or heterotrophic

Bacterial Sub-Classifications

types of bacteria