Changes in the Activity of Certain Enzymes of Hartmannella (Culbertson strain A‐1) During Encystment*

SYNOPSIS. Hartmannella (Culbertson strain A‐1) was found to undergo encystment (80–90% in 72 hr) on a non‐nutrient agar containing 0.015 M MgCl2 and 0.02 M taurine. Encystment was completely inhibited by 1 × 10−5 M Mitomycin C, or 1 × 10−7 M cycloheximide or 1 × 10−6 M Actinomycin D. The ability of the amoebae to consume glucose increased fourfold within 24 hr incubation in this medium. The specific activities of cellulose synthetase, hexosephosphate transaminase and uridine diphosphosphoglucose pyrophosphorylase were also stimulated. Dehydrogenases mediating electron transfer from pyruvate, malate, succinate, α‐ketoglutarate and α‐glycerophosphate to triphenyltetrazolium and from glucose‐6‐phosphate to nicotinamide‐adenine dinucleotide phosphate were, however, repressed during this period of incubation in the encystment medium. The results suggested that, during encystment of Hartmannella A‐1, there was a metabolic switchover and the enzyme machinery of the amoeba was oriented more towards biosynthesis of cyst wall constituents than towards the aerobic breakdown of carbohydrates.