pH has a major influence on the response of antibiotics upon. indicator microorganisms. The experiments were performed with different pH buffers. Buffer solutions of different pH were prepared by dissolving various quantities of K. 2 HPO 4 and KH 2 PO 4 in sufficient Milli-Q water. The pH was adjusted with 8 M. phosphoric acid or 10 M potassium hydroxide and sterilized in Autoclave.