Morphological characterization of the Serratia marcescens bacteriophage SLP

Genome organization and characterization of the virulent lactococcal phage 1358 and its similarities to Listeria phages

Virulent phage 1358 is the reference member of a rare group of phages infecting Lactococcus lactis. Electron microscopy revealed a typical icosahedral capsid connected to one of the smallest noncontractile tails found in a lactococcal phage of the Siphoviridae family. Microbiological characterization identified a burst size of 72 virions released per infected host cell and a latent period of 90 min. The host range of phage 1358 was limited to 3 out of the 60 lactococcal strains tested. Moreover, this phage was insensitive to four Abi systems (AbiK, AbiQ, AbiT, and AbiV). The genome of phage 1358 consisted of a linear, double-stranded, 36,892-bp DNA molecule containing 43 open reading frames (ORFs). At least 14 ORFs coded for structural proteins, as identified by SDS-PAGE coupled to liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses. The genomic organization was similar to those of other siphophages. All genes were on the same coding strand and in the same orientation. This lactococcal phage was unique, however, in its 51.4% GC content, much higher than those of other phages infecting this low-GC Gram-positive host. A bias for GC-rich codons was also observed. Comparative analyses showed that several phage 1358 structural proteins shared similarity with two Listeria monocytogenes phages, P35 and P40. The possible origin and evolution of lactococcal phage 1358 is discussed.

Serratia entomophila bacteriophages: host range determination and preliminary characterization

Eight bacteriophages specific to Serratia entomophila, a commercially available bacterial pathogen of the New Zealand grass grub (Costelytra zealandica), were characterized by host range determination, morphology and restriction endonuclease patterns of DNA. Phages were originally isolated from grass grub larvae and fermenter broth where phages had disrupted large-scale production of S. entomophila. Seven of the phages (CW1-CW5, BC, and BT) had heads similar in size (approximately 60 x 60 nm) and long noncontractile tails (185 x 10 nm). Phage AgRP8 (P8) had a smaller head and a short tail structure. Restriction endonuclease analysis divided the phages into four groups: CW2, CW4, CW5, BC, and BT gave identical patterns, white CW1, CW3, and P8 each gave different patterns. Six distinct phage groups were distinguished by host range determination, after screening phages against 70 bacterial isolates: CW1, CW2/CW4, CW3, CW5, BC/BT, and P8. While confirming the indicated groupings by DNA analysis, it was possible to distinguish between some of the phages in the largest group: CW2/4 could be distinguished from CW5 and BC/BT. Screening of soil bacterial isolates of S. entomophila against nondiluted phages will aid in monitoring the establishment and persistence of strains applied for biological control of the grass grub.