Genome sequence of temperate bacteriophage Psymv2 from Antarctic Dry Valley soil isolate Psychrobacter sp. MV2.

A temperate phage, Psymv2, was isolated from an Antarctic soil bacterium, Psychrobacter sp. MV2. The morphology of Psymv2 was typical of the Siphoviridae, with an isometric head and non-contractile tail. The Psymv2 genome was found to be 35,725 bp in length, had a G + C content of 44.5 %, with 49 protein-coding genes and one tRNA gene predicted. Integration of Psymv2 occurred at an ssrA gene, with the last 27 bases of this gene directly repeated at the prophage ends. The genome was organised in a modular fashion: integration, regulation, packaging, head assembly, tail assembly, host specificity and lysis. While the genome sequence had little similarity on a nucleotide level to previously reported phage sequences, the genome architecture resembled that of Siphoviridae of low G + C Gram-positive bacteria. The closest relatives to Psymv2 were uncharacterized putative prophages within the P. arcticus 273-4 and Acinetobacter baumannii 6013113 genomes. Global alignment of the Psymv2 genome and these prophages revealed significant conservation of the structural modules despite the large spatial divergence of their hosts. A number of unique ORFs were identified in the Psymv2 genome that may contribute to phage and lysogen fitness.