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Isolation and Characterization of an Extracellular Polysaccharide from Physarum polycephalum
J J McCormick1, J C Blomquist, H P Rusch
1McArdle Laboratory for Cancer Research, University of Wisconsin Medical School, Madison, Wisconsin 53706.
Abstract:
The myxomycetes are called slime molds because of the synthesis of copious amounts of extracellular material (slime) during parts of the life cycle. In Physarum polycephalum, small amounts of slime are produced during exponential growth of microplasmodia in shake flasks, but the amount of this slime increased 10- to 20-fold at 16 to 34 hr after microplasmodia were induced to form spherules by transferring them to salt solution. The slime obtained during both periods is the same; an acidic polysaccharide consisting of galactose, sulfate, and trace amounts of rhamnose. Analysis of the galactose-to-sulfate ratio gave a value of about 4 to 1. Infrared spectroscopy showed increased absorbance at 820 cm(-1) characteristic of C-O-S vibrations. Electrophoresis on polyacrylamide gel revealed that the material moved as a single band which stained with Alcian Blue and periodic acid Shiff reagent. However, fractionation of identical material on Dowex columns and electrophoresis on cellulose acetate showed the slime to be made up of three major fractions. The polysaccharide appeared as an extracellular capsule closely adhering to the walls of the spherules. It could be separated from the wall by vigorous shaking. The increased synthesis of slime during spherulation was not blocked by cycloheximide, suggesting that new enzyme synthesis was not necessary for its formation.
Insights
Slime molds like Physarum polycephalum produce more extracellular slime when forming spherules. This slime is an acidic polysaccharide, and its increased production during spherulation doesn't require new enzyme synthesis.
Area of Science:
- Mycology
- Biochemistry
- Cell Biology
Background:
- Myxomycetes, or slime molds, are known for producing extracellular slime.
- Physarum polycephalum is a model organism for studying slime mold biology.
Purpose of the Study:
- To investigate the composition and synthesis of extracellular slime in Physarum polycephalum during spherule formation.
- To determine if increased slime production during spherulation requires de novo enzyme synthesis.
Main Methods:
- Culturing Physarum polycephalum microplasmodia and inducing spherule formation.
- Analyzing slime composition using infrared spectroscopy, electrophoresis, and column fractionation.
- Treating cultures with cycloheximide to assess its effect on slime synthesis.
Main Results:
- Slime production increased 10- to 20-fold during spherule formation.
- The slime is an acidic polysaccharide composed mainly of galactose and sulfate (ratio ~4:1), with trace rhamnose.
- Electrophoresis showed the slime as a single band, but fractionation revealed three major components.
- Cycloheximide did not inhibit the increased slime synthesis during spherulation.
Conclusions:
- Physarum polycephalum significantly increases extracellular slime production when transitioning to spherules.
- The slime is a complex acidic polysaccharide, with its synthesis during spherulation potentially independent of new enzyme synthesis.
