Characterization and Genomic Analyses of dsDNA Vibriophage vB_VpaM_XM1, Representing a New Viral Family

Abstract

Background Vibrio parahaemolyticus has been a leading cause of foodborne disease outbreaks and infectious diarrhea cases in coastal areas, antibiotic resistance has increased significantly due to widespread antibiotic abuse, bacteriophages (phages) are viruses that specifically infect bacteria, it is necessary to isolate and characterize new phages to broaden our understanding of the ecology, evolution, and diversity of both phages and their bacterial hosts further. Results A novel vibriophage vB_VpaM_XM1 (XM1) was described in the present study. The morphological analysis revealed that phage XM1 had Myoviridae-like morphology, with an oblate icosahedral head and a long contractile tail. The genome size of XM1 is 46,056 bp, with a G + C content of 42.51%, encoding 69 open reading frames (ORFs). Moreover, XM1 showed a narrow host range only lysing Vibrio xuii LMG 21346 (T) JL2919, Vibrio parahaemolyticus 1.1997, and Vibrio parahaemolyticus MCCC 1H00029 among the tested bacteria. One-step growth curves showed that XM1 has a 40-minute latent period and 264 plaque-forming units (PFU)/cell burst size. In addition, XM1 exhibited broad pH, thermal, and salinity stability, as well as strong lytic activity, even at a multiplicity of infection (MOI) of 0.001. Multiple genome comparisons and phylogenetic analyses showed that phage XM1 is grouped in a clade with three other phages, including Vibrio phages Rostov 7, X29, and phi 2, and is distinct from all known viral families that have ratified by the standard genomic analysis of the International Committee on Taxonomy of Viruses (ICTV). Conclusions Therefore, the above four phages might represent a new viral family, tentatively named Weiviridae. The broad physiological adaptability of phage XM1 and its high lytic activity and host specificity indicated that this novel phage is a good candidate for being used as a therapeutic bioagent against infections caused by certain Vibrio parahaemolyticus strains.