Isolation and characterization of polysheaths, phage tail-like defective bacteriophages of Alcaligenes eutrophus H 16

Polysheaths were spontaneously formed inside cells of the hydrogen bacterium Alcaligenes eutrophus H 16. These particles are long tube-like structures of 24 nm diam. belonging to the phage tail-like defective bacteriophages (Lotz, 1976). In mid log-phase fermenter-grown cells, polysheaths were observed in about 20% of all cells sectioned. Evidence is provided for an inhibition of cell fission by polysheaths. Polysheaths were isolated by differential centrifugation and precipitation techniques using PEG and antibodies. The morphology of polysheaths was investigated electron microscopically by negative staining, ultrathin sectioning and metal shadowing. A surface lattice of the polysheath was derived from light optical diffraction data. The particles were also characterized by their biochemical and biophysical features: mol. wt. of the subunit determined by SDS-gel electrophoresis (58 000), amino acid composition, isoelectric point (4.4), u.v. absorbance spectrum indicating the absence of nucleic acid, buoyant density (1.258), and stability against denaturants and proteolytic enzymes.