Biological Characteristics and Genomic Analysis of a Lytic Phage phiP4-3 Specific for Proteus penneri
Background:Proteus penneri is an important bacterial pathogen,and the emergence of the multidrug resistant strains poses a major threat to public health and food safety.Phages can kill the host bacterial pathogens and are possible alternatives to conventional antibiotics.Objective:In this study,a lytic phage phiP4-3 was isolated from the gastrointestinal contents of freshwater fish using a Proteus penneri strain as an indicator.Phage phiP4-3 was investigated for biological characteristics,genomics,and taxonomy.Methods:The morphology of phiP4-3 was analyzed by transmission electron microscope(TEM);the bactericidal effect of phage was analyzed by one-step growth curve and bacteriostatic curve;the function and classification of phages were analyzed by genome sequencing and comparative genomics.Results:Through TEM observation,the head diameter of phiP4-3 bacteriophage is 98.83 nm,and the retractable tail length is 55.35 nm.The results of the one-step growth curve show that the incubation time of the phage is about 25 min,and its burst size was about 17 PFU/infection center.The antibacterial curve results showed that phiP4-3 can effectively inhibit the growth of the host.The genome sequencing assembly results showed that the genome length of phiP4-3 was 167 849 bp,with a GC content of 31.5％.Bioinformatic tools reveal that the phiP4-3 genome has 270 ORFs and 8 tRNA genes,and no antibiotic resistance genes or virulence genes were identified.Based on the classification results of comparative genomics,taxonomy,and ICTV,the phiP4-3 can be classified in the family Straboviridae and genus Bragavirus.Conclusion:A phage from Proteus penneri was isolated,and its biological characteristics and genomics were analyzed,providing a theoretical basis for the application of bacteriophage in public health and food safety.
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