Abstract: Taking Escherichia coli (E. coli) K1 strain DE058 as a host, a virulent phage PNJ1809-36 was isolated from chicken feces. The biological characteristics and genome analysis of this phage were studied. Phage PNJ1809-36 was isolated and purified, whereafter, the biological characteristics of the phage were studied by analyzing the morphology, optimal MOI, one-step growth curve, temperature and acid-base tolerance, and lysis curve in vitro. Moreover, the whole genome of the phage was sequenced and analyzed. The results showed that phage PNJ1809-36 formed transparent plaque with a clear boundary. Under microscopy, phage PNJ1809-36 presented a contractile tail, indicating that it belongs to Myoviridae. The result of host range test showed that phage PNJ1809-36 specifically targeted E. coli with K1 capsule. The optimal MOI of phage PNJ1809-36 was 0.01. One-step growth curve showed that the latent and explosive period was 10 min and 40 min, respectively. Phage was stable at 40 and 50℃, while lost activity at 60℃ for 30 min. Phage PNJ1809-36 could maintain activity under conditions of pH 3-11, with the optimal pH 6; The lysis curve showed that the phage could continuously inhibit the growth of host bacteria for 6 h. Genomic analysis showed that it had low sequence identity with early reported E. coli K1-specific phage, such as K1F and K1E, but presented over 90% sequence homology with newly discovered E. coli K1-specific phage at nucleic acid level, such as nepoznato, PVP-SE1, and phAPEC8. PNJ1809-36, a lytic phage targeting E. coli K1, belongs to a new phylogenetic branch of Myoviridae. Due to the specificity to E.coli K1, phage PNJ1809-36 has the potential to identify and control the diseases caused by E. coli K1.

Key words: phage, K1 capsule, Escherichia coli, biological characteristic, genome-wide analysis