Ref ID : 4251
Jytte Reichstein Nilsson; Structural Aspects of Digestion of Escherichia coli in Tetrahymena. J.Protozool. 34(1):1-6, 1987
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Tetrahymema pyriformis ingested Escherichia coli for 15-20 min and the fine structure of food vacuoles was analyzed 5, 15, 30, 60, 90, 120, and 180 min after uptake began. From this analysis, eight vacuolar stages could be defined, and three to four stages were found in each sample. Stage 1 represented forming and newly detached vacuoles with a random distribution of bacteria. Stage 2 is the "dehydration" vacuole in which the bacteria are compacted and a few may lyse. Stage 3, corresponding to the acid phosphatase-positive stage, has an electron-dense vacuolar matrix revealing components by lysed bacteria and the translucent coat of intact bacteria. Sage 4 is the "halo" stage where centrally located, intact bacteria are surrounded by lysed material being removed by pinocytic activity of the vacuolar membrane. Stage 5 represents lysis of bacteria remaining intact until this stage; the stage is apparently followed by a second stage 4. Stage 6 contains few bacterial profiles in a smeared homogeneous mass. Stage 7 contains numerous vesicular membranous structures which apparently become transferred to the cytoplasm as such. Stage 8 represents defecation vacuoles derived from fusion of smaller vacuoles. The main findings are as follows: I) Bacterial lysis may occur during acidification of the vacuole prior to fusion with lysosomes. II) Digestion of bacteria apparently occurs in "bursts" as indicated by the extended time that vacuoles in stage 4 and 5 are present. III) Bacterial membranous structures seem to be transferred directly to the cytoplasm of Tetrahymena. IV) Mass defecation occurs 2 hr after uptake begins.