Preliminary characterisation of bacteriophages of Serratia entomophila

C.R. WILSON, T.A. JACKSON AND H.K. MAHANTY. 1993. Bacteriophage was found for the first time associated with the bacterium Serratia entomophila, a pathogen of the New Zealand grass grub (Costelytra zealandica). Phage was isolated from the homogenized guts of field‐collected grass grubs from sites throughout New Zealand. The main phage type, φCW1, produced opaque plaques in sensitive bacterial lawn and had a lamboid structure consisting of an icosahedral head (55 nm) and a long non‐contractile tail (175 times 17 nm) with a bar across the base of the tail. Nucleic acid from φCW1 was digested to nucleotides by DNAse, suggesting double stranded DNA. On further examination of the homogenates, five phage types, φCW1‐5, could be distinguished on the basis of plaque morphology. Bacterial host range was determined by testing against a selection of Serratia spp. and other bacteria. All five phage types lysed Ser. entomophila only. Differences in susceptibility to the phage types were found within this species. Lysogeny was demonstrated in φCW1 by immunity to superinfection and induction of free bacteriophage from suspected lysogens. A restriction map for φCW1 was determined with BamHI, EcoRI and HindIII and a postulated origin of replication (ori) and cohesive site (cos) was suggested. The possible implications of bacteriophage on the use of Ser. entomophila as a biological control agent are discussed. Copyright © 1993, Wiley Blackwell. All rights reserved