Isolation and characterization of a novel lytic cold-active bacteriophage VNPH-1 from the Napahai wetland in China

Wetlands have unique characteristics and play a number of roles in the environment, principally in water purification, flood control, and the maintenance of shoreline stability. In this work, a lytic cold-active bacteriophage designated VNPH-1 was isolated from the Napahai wetland in China together with Aeromonas sobria NPH-1 cells, and a preliminary characterization of this bacteriophage was carried out. Electron microscopy revealed that VNPH-1 had an icosahedral head (116.7 nm) and a contractile tail (10 nm in width, 166.7 nm in length). Bacteriophage VNPH-1 was classified as Myoviridae and had an approximate genome size of 110 to 120 kb. One-step growth curve revealed that the latent and burst periods were 20 and 10 min, respectively, with an average burst size of 80 bacteriophage particles per infected cell. The pH and thermal stability of bacteriophage VNPH-1 were also investigated. The maximum stability of the bacteriophage was observed at an optimal pH of 9.0, and the phage was comparatively stable at pH 5.0-10.0. The specificity of this bacteriophage for its host makes it an attractive candidate for phage therapy of A. sobria infections. As VNPH-1 is a cold-active bacteriophage with a low production temperature, it would be worthwhile to characterize it further and to deepen knowledge of its interaction with A. sobria in future studies.