Some properties of Erwinia amylovora bacteriophages.
Eleven bacteriophages isolated from aerial parts of apple trees in Mich. orchards during 1975-76 were placed in 2 groups on the basis of morphology and serology. Group 1 produced 2 plaque types: PEal(h), 2-3 mm diam., surrounded by an expanding, translucent halo and PEal(nh), 1-2 mm, without a halo. Group II (PEa7) produced 0.5-1 mm diam. plaques with an expanding, translucent halo. PEal(h) was polyhedral, 60 nm diam. with a spike-like tail; PEa7 had an octahedral head, 75 nm diam. with a rigid, striated tail 135 nm long. PEal(h) and PEal(nh) had a buoyant density of 1.53 g/cc and a sedimentation coefficient of 566 S. PEa7 had a buoyant density of 1.44 g/cc with a sedimentation coefficient of 1037 S. The latent period of PEal(h) was 45 min with a burst size of 50 plaque forming units (pfu)/productive cell; that of PEa7 was 100 min with 8 pfu/productive cell. PEal(h) and PEal(nh) required 10 min at 55 deg C for complete thermal inactivation; 10 min at 65 deg were required for PEa7. Host ranges for the 2 groups were limited to E. amylovora and several E. herbicola strs. PEal(h) adsorbed more rapidly to encapsulated than to nonencapsulated strs. of E. amylovora but PEa7 adsorbed more rapidly to nonencapsulated strs.