Synthetic engineering and biological containment of bacteriophages.

The serious threats posed by drug-resistant bacterial infections and recent developments in synthetic biology have fueled a growing interest in genetically engineered phages with therapeutic potential. To date, many investigations on engineered phages have been limited to proof of concept or fundamental studies using phages with relatively small genomes or commercially available "phage display kits". Moreover, safeguards supporting efficient translation for practical use have not been implemented. Here, we developed a cell-free phage engineering and rebooting platform. We successfully assembled natural, designer, and chemically synthesized genomes and rebooted functional phages infecting gram-negative bacteria and acid-fast mycobacteria. Furthermore, we demonstrated the creation of biologically contained phages for the treatment of bacterial infections. These synthetic biocontained phages exhibited similar properties to those of a parent phage against lethal sepsis in vivo. This efficient, flexible, and rational approach will serve to accelerate phage biology studies and can be used for many practical applications, including phage therapy.

Staphylococcal Phage in Combination with Staphylococcus Epidermidis as a Potential Treatment for Staphylococcus Aureus-Associated Atopic Dermatitis and Suppressor of Phage-Resistant Mutants.

Atopic dermatitis is accompanied by the abnormal overgrowth of Staphylococcus aureus, a common cause of skin infections and an opportunistic pathogen. Although administration of antibiotics is effective against S. aureus, the resulting reduction in healthy microbiota and the emergence of drug-resistant bacteria are of concern. We propose that phage therapy can be an effective strategy to treat atopic dermatitis without perturbing the microbiota structure. In this study, we examined whether the S. aureus phage SaGU1 could be a tool to counteract the atopic exacerbation induced by S. aureus using an atopic mouse model. Administration of SaGU1 to the back skin of mice reduced both S. aureus counts and the disease exacerbation caused by S. aureus. Furthermore, the S. aureus-mediated exacerbation of atopic dermatitis with respect to IgE plasma concentration and histopathological findings was ameliorated by the application of SaGU1. We also found that Staphylococcus epidermidis, a typical epidermal symbiont in healthy skin, significantly attenuated the emergence of SaGU1-resistant S. aureus under co-culture with S. aureus and S. epidermidis in liquid culture infection experiments. Our results suggest that phage therapy using SaGU1 could be a promising clinical treatment for atopic dermatitis.

Lysogenisation of Shiga toxin-encoding bacteriophage represses cell motility.

Bacteriophages are genetic elements that play key roles in the evolution and diversification of bacterial genomes. The Shiga toxin (Stx)-encoding phage plays an important role in the horizontal transfer of the stx gene. However, the influence of the Stx phage integration on the physiological properties and gene expression pattern of the host have not been clearly resolved. In this study, we constructed the Sp5 lysogen through lysogenisation of E. coli K-12 by Sp5, an Stx2 phage in enterohaemorrhagic E. coli (EHEC) O157:H7 Sakai, and examined the effect of the resulting lysogen on cell motility under various growth conditions. Sp5 lysogenisation decreased cell motility and the expression of fliC, which encodes flagellin, under anaerobic conditions at 37°C. Sp5 also lowered the expression of fliA, which encodes the FliA-sigma factor responsible for the transcription of fliC, and flhD, which facilitates the expression of fliA. Sp5 lysogenisation reduced the amount of FlhD and FlhC expressed from the araBAD promoter, suggesting that one or more genes present in Sp5 represses flhDC at the post-transcriptional level. Flagellin is highly antigenic and triggers an immune response in the host. Thus, Sp5 might enhance its viability by repressing the expression of the flagellar regulon to circumvent the immune response of host cells.