CHARACTERIZATION OF A HIGHLY RESISTANT BIOMACROMOLECULAR MATERIAL IN THE CELL-WALL OF A MARINE DINOFLAGELLATE RESTING CYST

The remarkable physical and chemical resistance of the organic cell wa lls enclosing resting cysts formed by several species of dinoflagellat es has long invited questions regarding their composition. Traditional ly, this resistance was thought to derive from the presence of ''sporo pollenin'', a term originally coined to describe the highly refractory substance found in the walls of pollen and shores of higher plants. T he lack of detailed chemical analyses of dinoflagellate materials, how ever, has left this practice open to question. Here we report the resu lts of the first rigorous chemical characterization of resting cyst wa lls produced by a dinoflagellate, the extant marine species Lingulodin ium polyedrum (formerly Gonyaulax polyedra). Resistant cell walls were isolated by sequentially treating cyst-producing laboratory cultures by solvent extraction, saponification, and acid hydrolysis. At each st age of processing, residues were characterized by light microscopy, FT IR microspectroscopy, elemental analysis, and direct (''in source'') t emperature-resolved mass spectrometry (DT-MS). Initial materials and f inal residues were further analyzed by Curie-point pyrolysis-gas chrom atography-mass spectrometry (Py-GC/MS) and cupric oxide (CuO) oxidatio n, Overall, our results indicate an absence of extended n-hydrocarbon chains which typify aliphatic macromolecules (''algaenans'') dominatin g the resistant fractions of other algae studied to date. In contrast the data suggest that the cell wall contains relatively condensed, pre dominantly aromatic structures, possibly cross-linked via carbon-carbo n or ether bonds. The presence of prist-l-ene among the most prominent pyrolysis products also suggests that bound tocopherols function as a dditional structural elements in the wall material(s). The L. polyedru m resting cyst cell wall thus appears to contain a biomacromolecular s ubstance that is distinct from both sporopollenin and aliphatic algaen ans. These findings help to further establish a chemical basis for the preservation potential of organic biomacromolecules, and illuminate p ossible chemical/functional relationships among highly refractory subs tances from diverse biological sources. (C) 1998 Elsevier Science Ltd. All rights reserved.