96. Roberts, E., Seagull, R. W., Haigler,
C., and R. M. Brown, Jr. 1982. Alteration of cellulose microfibril
formation in eukaryotic cells: Calcofluor White interferes with
microfibril assembly and orientation in Oocystis apiculata.
Protoplasma 113:1-9.
96. Summary
Calcofluor White ST is a fluorescent brightener
that has previously been shown to alter cellulose ribbon assembly
in the bacterium Acetobacter xylinum. In this report,
we demonstrate that Calcofluor also disrupts cell wall assembly
in the eukaryotic alga Oocystis apiculata. When
observed with polarization microscopy, walls altered by Calcofluor
show reduced birefringence relative to controls. Electron microscopy
has shown that these altered walls contain regions which consist
primarily of amorphous material and which generally lack organized
microfibrils. We propose that wall alteration occurs because
Calcofluor binds with the glucan chains polymerized by the cellulose
synthesizing enzymes as they are produced. As a consequence,
the glucan chains are prevented from co-crystallizing to form
microfibrils. Synthesis of normal walls resumes when Calcofluor
is removed, which is consistent with our proposal that Calcofluor
acts by direct physical interaction with newly synthesized wall
components. Several types of fluorescent patterns at the cell
wall/plasmalemma interface have also been observed following Calcofluor
treatment. Fluorescent spots, striations, helical bands, and
lens-shaped thickenings have been documented. Each of these patterns
may be the result of the interaction of Calcofluor with cellulose
at different spatial or temporal levels or from varying concentrations
of the brightener itself. Helical bands and lens-shaped thickenings
also have been examined with the electron microscope. Like other
regions of wall alteration, they are found to contain primarily
amorphous material. Finally, we note that cells with severely
disrupted walls are unable to complete their normal life cycle.