COMPOSITION OF THE SHEATH OF SPHAEROTILUS NATANS.

Romano, Antonio H. (University of Cincinnati, Cincinnati, Ohio) and Joyce P. Peloquin. Composition of the sheath of Sphaerotilus natans. J. Bacteriol. 86:252-258. 1963.-The sheath of Sphaerotilus natans was isolated and subjected to chemical analysis. Isolation of the sheaths was accomplished by incubating cells in the presence of lysozyme and ethylenediaminetetraacetic acid in tris(hydroxymethyl)aminomethane buffer and adding sodium dodecyl sulfate subsequently. Under these conditions, there was complete dissolution of cells. The sheaths, which were left intact by this treatment, were recovered by centrifugation, washed exhaustively, lyophilized, and subjected to analysis. Hydrolysis of the sheath material with 2 n HCl at 100 C resulted in the liberation of reducing sugars amounting to 36% of the dry weight. Amino sugar accounted for 11% of the dry weight. Paper chromatography of hydrolysates showed the presence of glucose and hexosamine. Tests for muramic acid were negative. In addition to carbohydrate, 27% protein and 5.2% lipid were found to be present. Fractionation studies indicated that essentially all of the polysaccharide was associated with a trichloroacetic acid-soluble fraction. The sheath is therefore considered to be a protein-polysaccharide-lipid complex, which is chemically and anatomically distinct from the cell wall and the slime layer. It is hypothesized that this unique structure may be related to the microcapsule found in many gram-negative bacteria, and may represent a structural specialization of this more common structure.