By Levi Clancy for Student Reader on

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Sacromastigophora is a phylum of very divergent Eukaryotes. They all have these features in common:

  • Endemic to US.

  • Facultative Anaerobes (carbohydrate metabolism is anaerobic)

  • Lack mitochondria

  • Extracellular Parasites. They dwell in the lumen and do not invade host cells. instead they adhere to the plasma membrane of host cells. They are cytotoxic by inflicting mechanical damage to host tissues)

  • Replicate and divide within the host by binary fission

  • Can be cultivated in axenic cultures in the laboratory

  • All are killed by Metronidazole (Flagyl) - a drug that selectively kills anaerobic cells

OrganismDiseaseMajor SymptomsSubphylumOverview
Giardia lambliaGiardiasisDiarrhea/DysenteryMastigophoraPrimary agent of non-bacterial diarrhea in US.
Entamoeba histolyticaAmoebiasisDiarrhea/Liver AbsessSarcodina1-5% infected in US.
Trichomonas vaginalisTrichomoniasisVaginitisMastigophora2-7 million infections annually in US.
G. lambliaE. histolyticaT. vaginalis
Life StagesTrophozoite
Resistant Cyst
Resistant Cyst
Trophozoite Only
No Cyst Form
HostMany MammalsHuman OnlyHuman Only
TransmissionIngestion of CystIngestion of CystSexual Intercourse
Liver Abscess
Vaginitis, PROM