Chemical analyses of cell walls from microcysts and microsclerotia of Physarum flavicomum; comparison to slime coat from microplasmodia

Abstract

Haploid microcysts and diploid microsclerotia of Physarum flavicomum Berk. are dormant phases of the life cycle surrounded by rigid cell walls. Microplasmodia are the actively growing diploid phase of the life cycle. Microplasmodia lack a cell wall but are covered by a constantly replenished slime coat which is secreted and accumulates in liquid growth medium. Chemical analyses of purified walls from microcysts and microsclerotia revealed the presence of polysaccharide, lipid, and protein as major components. The polysaccharide of microcyst walls was composed of galactosamine with smaller amounts of glucose, galactose, and ribose. The polysaccharide of microsclerotial walls was primarily composed of galactosamine, with small amounts of glucose and galactose. The slime coat of microplasmodia consisted of a galactose-containing polysaccharide and protein. The protein components of microcyst and microsclerotial walls and the slime coat protein had strikingly similar amino acid compositions. Lysine was present in the greatest quantity, with large amounts of aspartic acid, alanine, glutamic acid, and glycine; the sulfur amino acids occurred in the smallest proportion.