Psychrobacter Phage Encoding an Antibiotics Resistance Gene Represents a Novel Caudoviral Family

Psychrobacter is an important bacterial genus that is widespread in Antarctic and marine environments. However, to date, only two complete Psychrobacter phage sequences have been deposited in the NCBI database. Here, the novel Psychrobacter phage vB_PmaS_Y8A, infecting Psychrobacter HM08A, was isolated from sewage in the Qingdao area, China. The morphology of vB_PmaS_Y8A was characterized by transmission electron microscopy, revealing an icosahedral head and long tail. The genomic sequence of vB_PmaS_Y8A is linear, double-stranded DNA with a length of 40,226 bp and 44.1% G+C content, and encodes 69 putative open reading frames. Two auxiliary metabolic genes (AMGs) were identified, encoding phosphoadenosine phosphosulfate reductase and MarR protein. The first AMG uses thioredoxin as an electron donor for the reduction of phosphoadenosine phosphosulfate to phosphoadenosine phosphate. MarR regulates multiple antibiotic resistance mechanisms in Escherichia coli and is rarely found in viruses. No tRNA genes were identified and no lysogeny-related feature genes were detected. However, many similar open reading frames (ORFs) were found in the host genome, which may indicate that Y8A also has a lysogenic stage. Phylogenetic analysis based on the amino acid sequences of whole genomes and comparative genomic analysis indicate that vB_PmaS_Y8A contains a novel genomic architecture similar only to that of Psychrobacter phage pOW20-A, although at a low similarity. vB_PmaS_Y8A represents a new family-level virus cluster with 22 metagenomic assembled viral genomes, here named Minviridae. IMPORTANCE Although Psychrobacter is a well-known and important bacterial genus that is widespread in Antarctic and marine environments, genetic characterization of its phages is still rare. This study describes a novel Psychrobacter phage containing an uncharacterized antibiotic resistance gene and representing a new virus family, Minviridae. The characterization provided here will bolster current understanding of genomes, diversity, evolution, and phage-host interactions in Psychrobacter populations.