Isolation, identification and biological properties of a lytic phage against Salmonella

Abstract:

[Objective] A lytic phage SLMP1 against Salmonella was isolated from the shellfish samples and identified, and its biological properties were assayed as well. [Methods] The lytic phage SLMP1 was isolated by the double-layer agar culture method. The phage plaque was observed and its host range was analyzed. Phage particles of SLMP1 were concentrated by precipitation with PEG8000 and purified by CsCl gradient centrifugation. The morphology of SLMP1 was observed by transmission electron microscopy. The genome of SLMP1 was extracted by phenol-chloroform method and the type of nucleic acid was identified with enzyme digestion analysis. The biological parameters including the thermal stability, pH stability, optimal multiplicity of infection (MOI) and the inactivation effects on the growth of Salmonella were assayed. [Results] The plaques of SLMP1 were round and transparent and their sizes were about 2–3 mm in diameter. SLMP1 can lyse Salmonella enterica subsp. Enteric and Salmonella typhimurium. SLMP1 had an icosahedral head approximately 62 nm in diameter and a long noncontractile tail with 110 nm in length. SLMP1 belongs to family Siphoviridae and is a dsDNA virus. SLMP1 was stable over a wide range of temperature (30–60 °C) and pH (4.0–11.0). The optimal MOI of SLMP1 was 0.001. One-step growth experiment showed that the latent time and burst time were 10 min and 120 min, respectively, and the burst size was 51. SLMP1 showed a good inactivation effects on the growth of Salmonella in broth. [Conclusion] SLMP1 is a dsDNA virulent phage and belongs to family Siphoviridae. The results indicated SLMP1 can serve as a promising biocontrol agent against Salmonella.