Revealing bacteriophage capabilities: pH and NaCl concentration effects on RSJ2 phage infectivity and stiffness

Abstract

The urgent necessity of reducing pesticides in the agricultural sector compels us to explore alternative, environmentally friendly approaches for controlling pathogenic bacteria and crop diseases. The usage of bacterial viruses or bacteriophages (phages) to control pathogenic bacteria is still limited due to the lack of understanding of the factors influencing shelf life. We examined the effects of pH and NaCl on the storage buffers on the infectivity of the RSJ2 phage. The RSJ2 phage infects Ralstonia solanacearum, causing bacterial wilt disease in tomatoes. The buffer that retained the highest phage titer (63 % after two months) was at pH 8.3 and 0.5 M NaCl. pH and NaCl concentrations directly affected the phage particles. The phage stiffness was measured with the nanoindentation technique, and a correlation between the phage remaining titers and the stiffness was revealed. The average stiffness associated with the highest remaining titer was 0.07 N/m, which falls into the intermediate stiffness range. The results agree with the previous study on the C22 phage stiffness, revealing an association between intermediate stiffness and phage infectivity. Phage stiffness can become an attribute of phage metastability and can be used to predict the phage shelf life.