Complete Genome Sequence of Pseudomonas aeruginosa Siphophage MP1412

GENOME ANNOUNCEMENT

Pseudomonas aeruginosa is a notorious nosocomial pathogen and causes fatal infections in immunocompromised individuals (2, 4, 8). Due to the emergence of multidrug-resistant P. aeruginosa strains, there is an urgent need for alternative antibacterial strategies to control P. aeruginosa infections. Phage therapy has been resurrected, as it has successfully treated experimental infections caused by P. aeruginosa in model animals (6). Hence, knowledge about the genetic diversity and antibacterial efficacy of P. aeruginosa phages needs to be explored.

A new phage (MP1412) was isolated from local sewage samples, forming distinguishable plaques on P. aeruginosa strain PAO1. Based on its virion structure, MP1412 is a Siphoviridae morphotype B2, like the previously characterized phages YuA and M6 (1, 3). It requires type IV pilus (TFP) for infection, but it could not infect P. aeruginosa strain PA14. To elucidate the phage genetic elements which are involved in the phage-host interaction and thus delineate the host spectra of these phages, we determined the complete genome sequence of MP1412.

Genomic DNA of MP1412, prepared as described previously (5), was sequenced using the GS FLX Titanium by the local service provider (Macrogen, Seoul, South Korea). The data processing was performed using Roche GS FLX software (version 2.6), and the open reading frames (ORFs) were predicted using GeneMark software (7). A homology search and a conserved domain analysis were carried out using BLASTP (http://www.ncbi.nlm.nih.gov/blast), and the potential presence of tRNAs were scanned using the tRNAscan-SE program (9).

Genomic analysis revealed that the 61,167-bp genome of MP1412 displays synteny to those of P. aeruginosa phages YuA (58,663 bp; GenBank accession number AM749441) and M6 (59,446 bp; GenBank accession number DQ163916), with 78 ORFs (gp01 to gp77 and gp60.1) and no tRNAs identified. Based on the homology, the genome of MP1412 can be divided into three functional regions: nucleotide metabolism and DNA synthesis (gp01 to gp23), host interaction (gp24 to gp44), and virion assembly and host lysis (gp45 to gp77). The presence of integrase (gp26) and a phage repressor (gp24) in the second region indicates that MP1412 undergoes a lysogenic cycle. MP1412 contains a GGDEF domain protein (gp43), which may function as diguanylate cyclase (DGC) to form cyclic di-GMP, a global second messenger controlling bacterial motility and sessility. Enhanced activity of DGC leading to an elevated cyclic di-GMP level plays an important role in the early stage of biofilm formation in P. aeruginosa (10). Unique to MP1412 is the presence of a hypothetical bacterial protein (gp46) and two homing DNA endonucleases (gp25 and gp53) of the GIY-YIG family. Based on their organization of the genomic regions, the roles of both endonucleases in the phage life cycle may differ. A deeper understanding of the organization and function of the unique phage proteins may provide a new perspective on the phage-host interaction in P. aeruginosa and lead to the development of new antibacterial targets with which to control the survival potential of this bacterium.