Phage therapy against bacterial pathogens has been resurrected as an alternative and supplementary anti-infective modality. Here, we observed that bacterial group motilities were impaired in Pseudomonas aeruginosa strain PA14 lysogens for some temperate siphophages; the PA14 lysogens for DMS3 and MP22 were impaired in swarming motility, whereas the PA14 lysogen for D3112 was impaired in twitching motility. The swarming and twitching motilities of PA14 were also affected in the presence of MP22 and D3112, respectively. The in vitro killing activities of D3112 and MP22 toward PA14 did not differ, and neither did their in vivo persistence in the absence of bacterial infections in mice as well as in flies. Nevertheless, administration of D3112, not MP22, significantly reduced the mortality and the bacterial burdens in murine peritonitis-sepsis and Drosophila systemic infection caused by PA14. Taken together, we suggest that a temperate phage-mediated twitching motility inhibition might be comparably effective to control the acute infections caused by P. aeruginosa. Pseudomonas aeruginosa causes a variety of infections, mostly in those who suffer from undesirable loss or abnormality in physicochemical or biological defense barriers against infections. Those include traumatic skin damage (burns), abnormal anatomy (some ear infections), abnormal secretion (cystic fibrosis), and compromised immunity. Several studies have revealed that clinical P. aeruginosa isolates from cystic fibrosis (CF) patients who suffer from persistent biofilm infections display a profound clonal diversity (20). Biofilm-mediated diversification may help enhance the ecological fitness of P. aeruginosa (2), even in the presence of conventional antibiotic therapy, which leads to the emergence of multiple-antibiotic-resistant bacterial clones (7, 17). Thus, physicians treating CF patients have been increasingly faced with infections caused by multiple-antibiotic-resistant isolates of P. aeruginosa. Such infections are generally treated by using two antibiotics together, which have different antibacterial mechanisms (6). The exploitation of this so-called antibiotic cocktail therapy is believed to increase the likelihood of therapeutic success through antimicrobial synergy (9,14).Renewed attention has been recently paid to phage therapy, which was proposed as an alternative or supplementary anti-infective modality to the conventional antibiotic therapy in controlling bacterial infections (8). Phages have been exploited to treat bacterial infections in Eastern Europe since the early 20th century (22). Phage therapy has been successful in humans for treating infectious diseases caused by various bacteria including Staphylococcus aureus, Streptococcus pneumoniae, Escherichia coli, Shigella, and Salmonella enterica, as well as P. aeruginosa (24). Furthermore, there is evidence for better therapeutic efficacy of phages than of antibiotics in that phages were successful in controlling biofilm-forming microorganisms such as P. aeruginosa, which are tolerant...

We report the complete genome sequence of Pseudomonas aeruginosa siphophage MP1412, which displays synteny to those of P. aeruginosa phages M6 and YuA. However, the presence of two homing endonucleases of the GIY-YIG family is unique to MP1412, suggesting their unique role in the phage life cycle of the bacterial host. 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-Y...