Huba L. Marton, Antonia P. Sagona, Peter Kilbride and Matthew I. Gibson

Poly(carboxylic acids) have been reported to inhibit phages’ ability to infect their bacterial hosts and hence offer an exciting route to discover additives to prevent infection. Here, we report the role of pH in inactivating phages to determine if the polymers are unique or simply acidic. It is shown that lower pH (= 3) triggered by either acidic polymers or similar changes in pH using HCl lead to inhibition. There is no inhibitory activity at higher pHs (in growth media). It is also shown that poly(acrylic acid) leads to reversible deactivation of phage, but when the pH is adjusted using HCl alone the phage is irreversibly deactivated. Further experiments using metal binders ruled out ion depletion as the mode of action.  These results show that polymeric phage inhibitors may work by unique mechanisms of action and that pH alone cannot explain the observed effects whilst also placing constraints on the practical utility of poly(acrylic acid).

RSC Applied Polymers. August 2024