Elucidation of the DNA synthetic cycle of Entamoeba spp. using flow cytometry and mathematical modeling

We developed a method to study the DNA synthetic cycles of Entamoeba histolytica and Entamoeba invadens by flow cytometry (FCM) based on a preparative procedure to reduce both high levels of natural fluorescence and non-specific adsorption of fluorochromes. We modeled G1, S, and G2 phases as a series of overlapping Gaussian curves. Both E. histolytica and E. invadens displayed G1, S, and G2 proportions that are consistent with eukaryotic cell populations in exponential or stationary growth phase. Exponential phase E. histolytica populations contained a hypodiploid subset with a mass of about 20% less than the diploid value which we estimate by FCM to be 24 x 10(-14) g DNA/cell. Exponential phase E. invadens populations contained a hypodiploid subset with a mass of about 6% less than the diploid value which we estimate by FCM to be 30 x 10(-14) g DNA/cell.