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BY2012 Microbiology Gallery of Amoeboid Protozoa
Amoeboid Protozoa• Unicellular protozoa move and feed by
means of cytoplasmic projections termed pseudopodia
• Amoeboid protozoa are characterised on the form and structure of their pseudopods
• Common in soils and aquatic habitats
• Entamoeba are both pathogens of and commensals in animals
• Dictyostelium (a slime mould) is a amoeba with a complex life cycle involving unicellular and multicellular phases
Amoeba proteus
Pseudopodium
PseudopodiumFood
vacuole
Contractile vacuole
Nucleus
Granular cytoplasm
Diagrammatic drawing of an amoeba
Amoeba proteus
Diagrammatic drawing of an amoeba
Amoeba proteus
Nomarski differential interference microcopy
Nucleus
Contractile vacuolePseudopodium
Food vacuoles
Amoeba proteus
Phase-contrast microscopy of an amoeba cell
Pseudopodia
Amoeba
Phase-contrast microscopy of a living amoeba cell
0.1 mm
Nucleus
Contractile vacuole
Food vacuoles
Amoeba proteus
Nomarski differential interference microscopy
Nucleus
Contractile vacuole
Food vacuoles
Pseudopodia
Amoeba proteus
Phase-contrast microscopy of a living amoeba cell
Contractile vacuole
Nucleus
Pseudopodia
Freshwater amoebae
Phase-contrast microscopy of amoebae
Freshwater amoeba
Phase-contrast microscopy of an amoeba
Freshwater amoeba
Phase-contrast microscopy of an amoeba
Amoeba
Excellent video of amoeba moving (WMV format):
http://www.dr-ralf-wagner.de/Amoeben_Sonnentierchen-englisch.html
Amoeba proteus
Time-lapse photographs of amoebic motility by pseudopod extension
Pfiesteria shumwayae Freshwater amoeba
Pfiesteria shumwayae amoebae engulfing a crytomonad (arrowed) [small freshwater flagellate protozoa] (A) and
showing two engulfed cryptomonads (B)
Metachaos gratum Freshwater amoeba
Nomarski differential interference microcopy
Amoeba proteus
Nucleus
Pseudopodium
Pseudopodium
Food vacuole
Stained Amoeba proteus
Amoeba proteus
Stained Amoeba proteus
Nucleus
Pseudopodia
Food vacuole
Amoeba proteus
Stained Amoeba proteus: A, nucleus; B, Pseudopodia; C, Food vacuole
CC
Entamoeba histolytica – Life Cycle
Entamoeba histolytica – Life Cycle
Ingestion by human of contaminated food
or water
Excystation in small intestine
Excretion in faeces
Encystment in colon
(amoebic) Liver
abscess(invasive)
Amoebic colitis
Asymptomatic colonisation
e e
h
f c
b
Cyst
a
g
Trophozoited
Entamoeba histolytica - Trophozoites
Following ingestion of cysts in faecally contaminated water or food, excystation occurs in the small intestine with the emergence amoeboid trophozoites which migrate to the large intestine
Ingested red blood cells
Ingested red blood cells
Nucleus
Nucleus
Entamoeba histolytica - Trophozoites
Stained Entamoeba histolytica trophozoite with ingested red blood cells (black arrows)
Nucleus
Entamoeba histolytica - Trophozoites
Trophozoites with intracellular and extracellular red blood cellsAnders Magnusson
Entamoeba histolytica - Cysts
Amoeboid trophozoites undergo encystment in the colon due to dehydration of faeces – immature cysts
have two nuclei, mature cysts have four nuclei
Nuclei
Mature cyst
cb = Chromatid bodies
Entamoeba histolytica - Encystment
1 Nucleus 2 Nuclei 4 Nuclei
Entamoeba - Cysts
Nuclei of cysts are arrowed
Entamoeba histolytica Mature Cysts
Nuclei are arrowed
Entamoeba dispar A non-pathogenic Entamoeba
Trophozoite Cyst with 4 nuclei
Nucleus
Entamoeba coli A non-pathogenic Entamoeba
Trophozoite Cyst has 8 nuclei
Nucleus
Life Cycle of Slime Mould Amoeba Dictyostelium
Life Cycle of Slime Mould Amoeba Dictyostelium
Single amoeboid cell Amoebae swarm together “Slug” of amoeboid cells
Dictyostelium discoides is an amoeba that lives in soil and moist leaf litter and belongs to the group termed slime moulds. Dictyostelium spores released from a mature fruiting body germinate forming amoebae. The amoebae feed on bacteria and reproduce by mitosis. When food runs out, the amoebae aggregrate forming a muticellular “slug”. The starvation stress induces expression of cell-cell adhesion glycoproteins on their surfaces, causing the amoebae to stick together.
Life Cycle of Slime Mould Amoeba Dictyostelium
Amoebae within the Dictyostelium slug differentiate, some forming the stalk of the fruiting body while others differentiate at the head of the stalk (sorus) into spores. The fruiting body comprises 50-80,000 cells.
Stalk
Basal disk
Sorus
Fruiting Body