Abstract
Structural changes during cell wall formation by populations of semisynchronously germinating zoospores were studied in the water mold Allomyces macrogynus. Fluorescence microscopy using Calcofluor white ST (which binds to β-1,4-linked glycans) demonstrated that Calcofluor-specific material was deposited around most cells between 2–10 min after the induction of encystment (beginning when a wall-less zoospore retracts its flagellum and rounds up). During the first 15 min of encystment there was a progressive increase in fluorescence intensity. Ultrastructural analysis of encysting cells showed that within 2–10 min after the induction of encystment small vesicles 35–70 nm diameter were present near the spore surface, and some were in the process of fusing with the plasma membrane. The fusion of vesicles with the zoospore membrane was concomitant with the appearance of electron-opaque fibrillar material outside the plasma membrane. Vesicles similar to those near the spore surface were found within the gamma (γ) particles of encysting cells. These particles had a crystalline inclusion within the electron-opaque matrix. During the period of initial cyst cell wall formation numerous vesicles appeared to arise at the crystal-matrix interface. Approximately 15–20 min was required for the cell wall to be formed. We suggest that the initial response of the zoospore to induction of encystment is the formation of a cell wall mediated by the fusion of cytoplasmic vesicles with the plasma membrane.
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Abbreviations
- GlcNac:
-
N-Acetylglucosamine
- DS:
-
sterile dilute salts solution
- PYG:
-
peptone-yeast extract-glucose broth
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Barstow, W.E., Pommerville, J. The ultrastructure of cell wall formation and of gamma particles during encystment of Allomyces macrogynus zoospores. Arch. Microbiol. 128, 179–189 (1980). https://doi.org/10.1007/BF00406156
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DOI: https://doi.org/10.1007/BF00406156