A T3 and T7 Recombinant Phage Acquires Efficient Adsorption and a Broader Host Range

Abstract

It is usually thought that bacteriophage T7 is female specific, while phage T3 can propagate on male and female Escherichia coli. We found that the growth patterns of phages T7M and T3 do not match the above characteristics, instead showing strain dependent male exclusion. Furthermore, a T3/7 hybrid phage exhibits a broader host range relative to that of T3, T7, as well as T7M, and is able to overcome the male exclusion. The T7M sequence closely resembles that of T3. T3/7 is essentially T3 based, but a DNA fragment containing part of the tail fiber gene 17 is replaced by the T7 sequence. T3 displays inferior adsorption to strains tested herein compared to T7. The T3 and T7 recombinant phage carries altered tail fibers and acquires better adsorption efficiency than T3. How phages T3 and T7 recombine was previously unclear. This study is the first to show that recombination can occur accurately within only 8 base-pair homology, where four-way junction structures are identified. Genomic recombination models based on endonuclease I cleavages at equivalent and nonequivalent sites followed by strand annealing are proposed. Retention of pseudo-palindromes can increase recombination frequency for reviving under stress.

Phage Therapy: a Step Forward in the Treatment of Pseudomonas aeruginosa Infections

“…Some of these bottlenecks are already being addressed by the introduction of molecular biology techniques that enable the genetic engineering of phage genomes. For example, phages have been genetically engineered to enhance their performance against biofilms (85), to improve antibiotic activity (86,87), and to expand their host ranges (88)(89)(90)(91). The use of well-defined and purified phage preparations is also crucial for therapeutic applications and for regulatory approval (83,92).…”

Genetically Engineered Phages: a Review of Advances over the Last Decade

“…The T3/7 recombinant phage exhibited a broader host range and a better adsorption efficiency than those of either of the wildtype phages, i.e., T3 and T7 (132). Le et al demonstrated that host specificity in P. aeruginosa phages is also tail fiber dependent (60).…”

Phage therapy: awakening a sleeping giant

“…Recent advances in sequencing technologies and genetic engineering have allowed for the design of phages with more predictable and domesticated therapeutic properties. For instance, recombinant phages can be created to have hybrid tail fibers from related phages to broaden bacterial host ranges [26,27]. Moreover, added genes can improve phage diffusion by expressing exopolysaccharide-degrading enzymes specific to target biofilm [26].…”