Characterization of Mycoplasmatales virus-laidlawii 3

Purified preparations of Mycoplasmatales virus-laidlawii 3 were negatively stained and studied by electron microscopy. They were seen to consist of uniform sized particles having a polyhedral head, 57 nm by 61 nm, and a short tail, 25 nm long, joined to the head at one vertex by a collar. The particles were shown to have buoyant densities of 1-477 g/ml in CsC1, 1-32 g/ml and 1-26 g/ml in potassium tartrate and a sedimentation coefficient, S20,W, OF 290 +/- 13. They are composed of 35-2% double-stranded DNA and five structural polypeptides with approximate mol. wt. of 172000, 81000 73000, 68000 and 43000. The classification of the virus from its morphology and chemical properties is discussed.