Summary
Myxamoebae ofDidymium iridis were removed from the bacterial food source and induced to encyst by transfer to 10 mM phosphate buffer. After 24 hours of induction approximately 90% of the myxamoebae had differentiated into microcysts. The kinetics of encystment were not significantly affected by pH or osmolarity of the encystment medium. Early stages of encystment were distinguished by the appearance of autophagic vacuoles and an extracellular “slime-like” sheath. The outer wall layer, consisting of dense fibrils, was unevenly deposited after 4 hours. An electron-lucent, second wall layer appeared between 5–10 hours followed by a densely packed, third wall layer adjacent to the plasma membrane. Wall formation appeared to involve smooth-membraned vesicles of possible Golgi origin. The vesicle contents and outer wall layer reacted with the periodic acid-silver methenamine stain for polysaccharide. The density of intramembrane particles of the protoplasmic fracture face increased during encystment with a gradual formation of aggregates of particles.
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References
Akins, R. A., Byers, T. J., 1979: Encystment enhancing activity produced byAcanthamoeba castellanii. J. Cell Biol.83, 21 a.
Aldrich, H. C., 1974: Spore cleavage and the development of wall ornamentation in two myxomycetes. Proc. Iowa Acad. Sci.81, 28–35.
—,Blackwell, M., 1976: Resistant structures in myxomycetes. In: The fungal spore (Weber, D. J., Hess, W. M., eds.), pp. 413–466. New York: J. Wiley.
Band, R. N., 1963: Extrinsic requirements for encystation by the soil amoeba,Hartmannella rhysodes. J. Protozool.10, 101–106.
Bartnicki-Garcia, S., Hemmes, D. E., 1976: Some aspects of the formation and function of oomycete spores. In: The fungal spore (Weber, D. J., Hess, W. M., eds.), pp. 593–641. New York: J. Wiley.
Branton, D., Bullivant, S., Gilula, N. B., Karnovsky, M. J., Moor, H., Mühlethaler, K., Northcote, D. H., Packer, L., Satir, B., Satir, P., Speth, V., Staehelin, L. A., Steere, R. L., Weinstein, R. S., 1975: Freeze-etching nomenclature. Science190, 54–56.
Dougherty, W. G., 1976: Freeze-fracture characterization of the plasmodial plasmalemma. M. S. Thesis, University of Florida.
Erdos, G. W., Hohl, H. R., 1980: Freeze-fracture examination of the plasma membrane of the cellular slime moldPolysphondylium pallidum during microcyst formation and germination. Cytobios29, 7–16.
Gorman, J. A., Wilkins, A. S., 1980: Developmental phases in the life cycle ofPhysarum and related myxomycetes. In: Growth and differentiation inPhysarum polycephalum (Dove, W. F., Rusch, H. P., eds.), pp. 157–202. Princeton: Princeton University Press.
Griffiths, A. J., 1970: Encystment in amoebae. Adv. in Microbial Physiol.4, 105–128.
Grove, S. N., Bracker, C. E., 1978: Protoplasmic changes during zoospore encystment and cyst germination inPythium aphanidermatum. Exper. Mycol.2, 51–98.
Haars, A., Zaar, K., Hüttermann, A., 1979: Induction of synchronous differentiation (encystment) inPhysarum polycephalum myxamoebae. Arch. Microbiol.120, 105–112.
Henney, Jr.,H. R., Chu, P., 1977 a: Differentiation ofPhysarum flavicomum: Metabolic patterns and the role of amino acids in the control of encystment. Exper. Mycol.1, 41–51.
Howard, F. L., 1931: The life history ofPhysarum polycephalum. Am. J. Bot.18, 116–133.
Koevenig, J. L., 1964: Studies on the life cycle ofPhysarum gyrosum and other myxomycetes. Mycologia65, 170–184.
Ling, H., Moore, D., 1979: Multinucleate cysts of the myxomyceteDidymium iridis. Mycologia71, 713–721.
Mims, C. W., 1972: Spore-wall formation in the myxomyceteArcyria cinerea. Trans. Br. Mycol. Soc.59, 477–481.
Müller, M., Meister, N., Moor, H., 1980: Freezing in a propane jet and its application in freeze-fracturing. Mikroskopie36, 129–140.
Patterson, M. A., Scheetz, R. W., 1977: Spherule wall formation inPhysarum polycephalum. Protoplasma92, 253–261.
Rambourg, A., 1967: An improved silver methenamine technique for the detection of periodic acid-reactive complex carbohydrates with the electron microscope. J. Histochem. Cytochem.15, 409–412.
Raub, T. J., Aldrich, H. C., 1981: Ultrastructural events and kinetics of microcyst germination in the myxomyceteDidymium iridis. Arch. Microbiol.128, 384–389.
Reynolds, E. S., 1963: The use of lead citrate at high pH as an opaque stain in electron microscopy. J. Cell Biol.17, 208–212.
Rhea, R. P., 1966: Electron microscopic observations on the slime moldPhysarum polycephalum with specific reference to fibrillar structures. J. Ultrastruct. Res.15, 349–379.
Schuster, F., 1965: Ultrastructure and morphogenesis of solitary stages of true slime molds. Protistologica1, 49–62.
Spurr, A. R., 1969: A low-viscosity epoxy resin embedding medium for electron microscopy. J. Ultrastruct. Res.26, 31.
Toama, M., Raper, K., 1967: Microcysts of the cellular slime moldPolysphondylium pallidum. I. Factors influencing microcyst formation. J. Bacteriol.94, 1143–1149.
Taylor, P., Kahn, A. J., 1969: Initiation of encystment in the mycetozoanProtostelium mycophaga. J. Protozool.16, 152–154.
Turner, H. M., Johnson, J., 1975 a: Transmission and scanning electron microscopy of changes associated with microcyst formation in the myxomycetePhysarum polycephalum. Cytobios12, 95–107.
— —, 1975 c: Ultrastructural changes associated with induction of microcyst formation by mannitol inPhysarum polycephalum amoebae. Cytobios13, 241–250.
Wilkinson, M. J., Northcote, D. H., 1980: Plasma membrane ultrastructure during plant protoplast plasmolysis, isolation and wall regeneration: A freeze-fracture study. J. Cell Sci.42, 401–415.
Zaar, K., Kleinig, H., 1974: Spherulation ofPhysarum poly-cephalum. I. Ultrastructure. Cytobiologie10, 306–328.
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Florida Agricultural Experiment Station Journal Series No. 3473.
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Raub, T.J., Aldrich, H.C. Microcyst formation in the plasmodial slime moldDidymium iridis . Protoplasma 112, 81–91 (1982). https://doi.org/10.1007/BF01280218
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DOI: https://doi.org/10.1007/BF01280218