S. Saidfernandez et al., ENTAMOEBA-HISTOLYTICA CYSTS WITH A DEFECTIVE WALL FORMED UNDER AXENICCONDITIONS, Parasitology research, 79(3), 1993, pp. 200-203
Axenic HK9 Entamoeba histolytica strain amoebae, maintained in PEHS me
dium, displayed several cystic characteristics that involve an active
process of cystic wall formation, cellular volume and density diminuti
on, and one or two nuclear divisions. The differentiation process was
asynchronic, beginning after the logarithmic growth phase. The axenic
cysts, which were maintained in a 50 mOsm/kg medium at 4-degrees-C for
72 h, produced growing trophozoites within 1 7 days of incubation at
36-degrees-C in fresh medium. Negative results were obtained with trop
hozoites submitted to the above treatment, and with axenic cysts maint
ained in double-distilled water at 4-degrees-C for 24 h, or in 0.1 % s
arkosyl, for 10 min at room temperature instead of 55 mosmol/kg medium
. Thus, the HK9 E. histolytica strain, cultured in PEHPS, produced und
er axenic conditions a small proportion of mature, metabolically activ
e cysts, but with an immature or abnormal wall.