Genome instability of Pseudomonas aeruginosa phages of the EL species: Examination of virulent mutants

Abstract

The article continues a study of pseudolysogeny in Pseudominas aeruginosa infected with phiKZ like phages of the EL species. Analysis was performed for several newly isolated vir mutants of EL phages (EL and RU) that were virulent (capable of causing lysis of bacteria infected with the wild type phage) and a lower extent of opalescence of negative colonies (NCs). Wile type recombinants were detected in crosses of virulent mutants of phages EL and RU to confirm the polygenic control of virulence. Since a deletion mutation was found in one of the virulent EL mutants and high genetic instability was characteristic of another mutant, a mobile genetic element was assumed to play a role in mutagenesis. Pseudolysogeny of bacteria provides for horizontal gene transfer between different bacterial strains. Hence, sequencing of the phage genome and demonstration of the lack of toxic gene products are insufficient for the phage to be included into a therapeu tic mixture. To use live phages, it is essential to study in detail the possible consequences of their interaction with host bacteria.

A Genetic Approach to the Development of New Therapeutic Phages to Fight Pseudomonas Aeruginosa in Wound Infections

“…Interestingly, phiKZ and EL behave like phages with repressors of different specificity (with phiKZ revealing dominance) [54], see Figure 2. Probably, the substitution of virulent mutants of phiKZ-like phages for wild type phages in therapeutic mixtures decreases the possibility of HGT [55,56]. …”

Modular Approach to Select Bacteriophages Targeting Pseudomonas aeruginosa for Their Application to Children Suffering With Cystic Fibrosis

“…The phiKZ-like group of giant phages infecting P. aeruginosa includes several species and are of interest not only because of their use in a therapeutic setting, but also as a unique model for the study of phage evolution and specific packaging of the genomic DNA ( Burkal’tseva et al, 2002 ; Mesyanzhinov et al, 2002 ; Krylov et al, 2003 , 2004 , 2005 , 2011 ; Hertveldt et al, 2005 ; Shaburova et al, 2008 ; Pleteneva et al, 2010 ; Sokolova et al, 2014 ). This group of Myoviridae phages includes several phage species that exhibit common properties of the type member phiKZ (particle size and morphology, the presence of an inner body in the capsid, and a specific packaging mechanism of phage genomic DNA).…”

“…Meanwhile phiCHE bacteriophage, closely related with phiEL, has been isolated from a bacterial strain in burn wound. Different mutations in genomes of phiEL-like phages influence the effect ( Krylov et al, 2011 ). This is manifested through the appearance of opalescence of bacterial growth ( Figure 3 ) and a significant increase in the final yield of phage.…”

Common Preconditions for Safe Phage Therapy of <i>Pseudomonas aeruginosa</i> Infections

“…Such unusual behavior could not be predicted after the sequencing and annotation phage genomes [27] [28] (Figure 1). We have isolated specific mutants of phiKZ-like phages where this feature has been lost [30]. Such mutants should replace wild-type phiKZ-like phages in therapeutic mixtures.…”

“…The most of the currently used phage mixtures include different phiKZ-like phages [25]- [30]. Bacteria in biofilms of P. aeruginosa after multiple infection with phiKZ-like phages enter pseudo lysogenic state and produce large amounts of mucous material obstructing access of phage particles to the bacteria in the wound [29].…”