Structure of Bacillus subtilis Bacteriophage φ29 and the Length of φ29 Deoxyribonucleic Acid

Abstract

Anderson, D. L. (University of Minnesota, Minneapolis), D. D. Hickman, and B. E. Reilly. Structure of Bacillus subtilis bacteriophage φ29 and the length of φ29 deoxyribonucleic acid. J. Bacteriol. 91:2081–2089. 1966—Bacillus subtilis bacteriophage φ29 were negatively stained with phosphotungstic acid. The head of φ29 has a hexagonal outline with a flattened base, and is about 315 A wide and 415 A in length. The virus has an intricate tail about 325 A in length. Twelve spindle-shaped appendages are attached to the lower of two collars which comprise the proximal portion of the tail. The distal 130 A of the tail axis has a diameter of about 60 A and is larger in diameter than the axis of the upper portion of the tail. Comparison of electron microscopic counts of φ29 with plaque-forming units indicated that about 50% of the microscopic entities were infective. Phenol-extracted φ29 deoxyribonucleic acid (DNA) molecules were prepared for electron microscopy by the cytochrome c film technique of Kleinschmidt et al. Measurement of contour lengths of DNA molecules from three preparations gave skewed distributions of lengths with observed modal class values ranging from 5.7 to 5.9 μ. Assuming that φ29 DNA is a double helix in the B form, the corresponding molecular weights would be 10.9 × 10⁶ to 11.3 × 10⁶ daltons. The largest DNA molecules would have a volume of 1.9 × 10⁷ A³ which is about 25% greater than the estimated 1.4 × 10⁷ A³ internal volume of the phage head. Images