Does Giardia intestinalis need glucose as an energy source?

Giardia intestinalis was grown in Diamond's TYI-S-33 medium containing either 50 mM-glucose or no added glucose to assess its dependence on glucose availability as an energy source. The parameters monitored included cell growth, glucose utilization and the accumulation of end products in the medium. In the medium containing no added glucose, G. intestinalis trophozoites achieved a cell density of about half that of the control, and produced the same end products, alanine, ethanol and acetate. Decreased amounts of both ethanol and alanine were observed (10 and 33% of controls, respectively after 4 days) while there was no change in acetate production. These observations indicate that G. intestinalis can utilize carbon sources other than glucose, and is not absolutely dependent upon glucose as an energy source.