Interaction of bacteriophage 1P with the cell surface components of Rhizobium trifolii 24SM

Phage 1P is a B RADLEY C type with an octahedron head 52 nm in diameter and a short tail 10.2 nm long. The process of phage adsorption in to the host cells has been studied. At first, virions attached themselves to the host exopolysaccharide (EPS) capsule, with subsequent penetration through the capsular layer towards the cell wall. Isolated EPS preparation, composed mainly of mannose, galactose and glucose did not neutralize the phages. The rate of attachment of phage 1P to the mucoid strain R. trifolii 24SM and to its nonmucoid, morphologically rough mutants, 24AR and 24R, is the same. The cell wall of R. trifolii 24SM contains lipopolysaccharide (LPS) receptors, which bind phage particles irreversibly. Purified LPS showed a PhI 50 value of 0.05 μg ml −1 . One particle of phase 1P is neutralized by 5 × 10 −16 g of LPS.