Ameba

• Protozoans


  • Eukaryotic organisms (possesses nucleus and organelles)
  • Varies in shape, size locomotion
  • Reproduce asexually (binary fission) or asexually and sexually (in Plasmodium species)
  • Do not possess cell walls (only found in bacteria, plants, and fungi)
  • Consist of nucleus and cytoplasm
• Nucleus


  • Genetic material
  • Contains nucleolus or karyosome (RNA material) or endosome
• Cytoplasm


  • Consists of 2 regions
  • Endoplasm: for metabolism and nutrition
  • Ectoplasm: hyaline (clear) structure for protection
• Sarcodina

  • Ameba
  • Possesses pseudopodia used for locomotion
  • Inhabits the large intestine except for E. gingivalis (inhabits the mouth/oral cavity)
  • Possess peripheral chromatin
  • Nucleus is vesicular (looks like it has holes or spaces inside)
  • All are commensal except E. histolytica
• Stages of development

  1. Trophozoite: motile or vegetative stage

  2. Cyst: nonmotile stage
• Trophozoite

  • Seen in watery, loose, or mucus-filled stool
  • Labile: breaks easily (especially in the absence of water)
  • Stains are added to visualize the nucleus
  • Buffered Methylene Blue (either Nair's or Quensel's)
  • Iodine is toxic in Trophozoite
• Cyst

  • Circular/round
  • Resistant
  • Infective stage for most ameba
  • Immature cyst: pre-cyst
  • Mature cyst: metacyst
  • Seen in formed stool (as stool is more formed, there are less trophozoites)
  • Stained with Lugol's Iodine (I2) and D'Antoni's Iodine