Entamoeba histolytica: changes in the zymodeme of cloned nonpathogenic trophozoites cultured under different conditions.

In this paper we report the occurrence of changes in the migration of certain isoenzymes of a cloned strain (MAV-CINVESTAV) of Entamoeba histolytica. This strain was isolated from an asymptomatic carrier and showed an initial nonpathogenic zymodeme I. The transfer of polyxenic trophozoites from Robinson's medium (7% serum) to Jones' medium (30% serum) provoked changes in isoenzyme expression, resulting in the conversion of zymodeme I to a zymodeme that was similar to the XVII zymodeme except for two slow-running bands and a single fast-running band that were detected for hexokinase (HK). This XVII-like zymodeme reverted to zymodeme I when trophozoites were cultured under monoxenic conditions in TY1-S-33 medium (10% serum). When we cultured cloned strain MAV-CINVESTAV under axenic conditions in TY1-S-33 medium, trophozoites expressed a pathogenic zymodeme with two fast-running HK bands and a beta-phosphoglucomutase band. In addition, phagocytosis and the ability of the trophozoites to destroy cell-culture monolayers were expressed only in trophozoites cultured under axenic conditions. The axenization procedure required the presence of live Fusobacterium symbiosum and is also described herein.