Characterization and depolymerase activity analysis of Acinetobacter baumannii bacteriophage vB_AbaP_IME546

In this study, we selected Acinetobacter baumannii Ab2897, a strain from our laboratory, as the host, while the lytic bacteriophage vB_AbaP_IME546 was isolated from untreated hospital sewage. We examined the phage's biological characteristics and found that its latent period was under 5 min, with complete lysis of the bacteria occurring within 60 min. The plaques formed by the bacteriophage showed a halo, indicating the presence of an antibacterial protein. Consequently, this phage underwent next-generation sequencing. A BLAST analysis of the assembled genome sequence indicated that vB_AbaP_IME546 is a novel bacteriophage. After carrying out RAST annotation, it was proposed that the tail fiber protein of the bacteriophage might possess depolymerase activity. To further explore this, the ORF49 gene encoding the tail fiber protein was cloned and expressed. The resulting protein, Dp49, was successfully generated. When the protein was applied to a double-layer plate assay, a transparent halo formed in the area surrounding the bacterial growth. This finding confirms that the IME546 phage exhibits depolymerase activity during the lysis of Ab2897.