Characteristics of ribosomes during differentiation from trophozoite to cyst in axenic Entamoeba sp

Sufficient numbers for biochemical investigations of Entamoeba invadens from each differentiated stage of the life cycle have been obtained in bacteria-free cultures. The ribosomes of the growing trophozoites were found to be monomers of 80S with 60S and 40S subunits which contained RNA of approximate molecular weights 1.4 × 10 6 and 0.70 × 10 6. The ribonucleoprotein microcrystals of the cysts break down into 83S monomers with 65S and 47S subunits which contain RNA with an unusually high content of G and U and approximate molecular weights 1.75 × 10 6 and 0.85 × 10 6. The 1.9 × 10 6 and 2.2 − 2.8 × 10 6 molecular weight components contaminated with DNA are unstable. Microcrystals appeared to contain mainly the higher molecular weight RNAs. These findings are discussed in relation to embryonic ribosome synthesis and microcrystals.