Isolation and Characterization of a Galactosamine Wall from Spores and Spherules of Physarum polycephalum

Abstract

The myxomycete, Physarum polycephalum , can be induced under laboratory conditions to form two different hard-walled forms, spores and spherules. Characterization of both types of walls revealed only a single sugar, galactosamine. It was identified after acid hydrolysis of the isolated walls by chromatography in three solvent systems, by its positive reaction with ammoniacal silver nitrate, ninhydrin, Galactostat, and the Elson-Morgan test, and by ninhydrin degradation to lyxose. Galactosamine was present as a polymer with solubility characteristics the same as the β1-4–linked glucosamine polymer (chitosan). The walls were also found to contain about 2% protein. Spherule walls revealed a single glycoprotein on gel electrophoresis. Spore walls contained a similar protein component. The phosphate content of isolated spherule walls was 9.8%, and that of spore walls was 1.4%. Spore walls also contained about 15% melanin which was shown to be similar to fungal melanin. A novel method was used to measure the rate of mature spherule formation based on the loss of extractability of P. polycephalum natural pigment. The presence of a rare galactosamine polymer in P. polycephalum spore and spherule walls as the only carbohydrate suggests that the myxomycetes are not closely related to the fungi or the protozoa.

Biochemical Events during Spherule Formation of Physarum polycephalum

“…The time of appearance and disappearance of the Golgi-apparatus coincides well with the maximal activity of slime production (MCCORMICK et al 1970a) and might support the view that this structure is envolved in the secretion of extracellular polysaccharides (RAM80URG et al 1969).…”

“…These carbohydrates have been studied in more details by MCCORMICK, who devised methods for the purification of both the slime and the cell wall. He identified the slime as a galactose polymer (with traces of rhamnose) in which every fourth unit is connected with sulfate (MCCORMICK et al 1970a).…”

Spore Ultrastructure of the Myxomycete Physarum polycephalum

“…2, 3). McCormick, Blomquist, and Rusch (1970) found the spore cell wall of this organism to contain mainly galactosamine but also some protein and melanin.…”

Morphogenesis and dynamics of slime molds in various environments

“…Indeed, in bacteria for instance, mucus is used as protective barrier for the cells against harsh external conditions (65). In slime molds, the extracellular mucus excreted by the slime molds can have different roles: hydrophilic shield to prevent water loss (66), a lubricating surface over which the slime molds can easily crawl (67), a defensive coat to protect against invasion by foreign materials and organisms (66,68), an aid to phagocytosis (69), a surface that promotes ion-exchange (66) and has externalized spatial memory that helps navigation in unknown environments (26,36,53). Here, we can add a new function for the mucus i.e.…”