Abstract: This study focuses on a strain of Salmonella Pullorum bacteriophage Pu29, comprehensively analyzing its biological and genomic characteristics. A magnetic separation and enrichment technology for Salmonella based on the phage Pu29 as a recognition element was established. The phage belongs to the genus Roufvirus and has an icosahedron head and an irreducible long tail. Pu29 has a wide host spectrum. The optimal adsorption rate of Pu29 on host cells was 88.67% at 15 min. One step growth showed a latent period of 30 min, an explosive period of 180 min, and an explosive amount of 115.74 PFU/cell. Meanwhile, Pu29 has good heat resistance (30-60 ℃) and pH tolerance (pH 4-11). The Pu29 genome consists of 45,715 bp (46.08% GC content) and 81 open reading frames (ORFs), including 18 ORFs with known functions that does not carry genes encoding toxicity or resistance factors. The probe PhagePu29-MBs were prepared by coupling the phage Pu29 with carboxylated nano magnetic beads (MBs) through amide reaction. When 25 μg probe was incubated with Salmonella at 37 ℃ for 20 min, the highest capture rate of Salmonella could reach 83.93%, and the lowest capture bacterial concentration was 45 CFU/mL. Transmission electron microscopy (TEM) was used to observe that the probe PhagePu29-MBs could specifically capture Salmonella. In the spiked samples, the highest capture rate of Salmonella separated and enriched by probe PhagePu29-MBs can reach 92.92%. The time for separating Salmonella using this method was approximately 30 min. Therefore, this study established a fast and highly specific magnetic separation method for Salmonella based on phage Pu29 and may lay the foundation for the development of a rapid phage-based method for the separation and enrichment of foodborne pathogens in food samples.

Key words: Salmonella, phage, biology characteristics, magnetic separation technology, rapid separation and enrichment