Cytoplasmic reserve polysaccharide of Selenomonas ruminantium

Selenomonas ruminantium accumulated large quantities of intracellular polysaccharide when grown in simple defined medium in a chemostat, particularly at low dilution rate under NH3 limitation when the carbohydrate content of the cells was greater than 40% of the dry weight. This polysaccharide was used as a source of energy under conditions of energy starvation. Abundant, densely staining cytoplasmic granules were observed by electron microscopy in sections stained by the periodic acid-thiocarbohydrazide-osmium technique. The polysaccharide was extracted in 30% KOH followed by precipitation with 60% ethanol and was found to be a glucose homopolymer. Sepharose 4B gel filtration and iodine-complex spectroscopy showed that the polysaccharide was of the glycogen type with a molecular weight of 5 X 10(5) to greater than 20 X 10(5) and an average chain length of 12 glucose residues.