Effect of valinomycin on ion transport in bacterial cells and on bacterial growth

The antimicrobial action of valinomycin relative to the K⁺ and Na⁺ contents of the medium has been investigated in several species of bacteria, particularly in Streptococcus faecalis, which effects energy-linked transport exclusively via degradation of glycolytic ATP, Micrococcus lysodeikticus, effecting active ion transport by respiration and Staphylococcus aureus, the energy-dependent ion transport of which is due to both glycolytic ATP degradation and respiration. It was demonstrated that valinomycin does not act on K⁺ transport in the glycolysing cells in the same manner as it does on respiring cells under similar conditions. Addition of valinomycin to respiring cells leads to an increase in K⁺ influx against the concentrational gradient in both growing and resting cells. In contrast to this, antibiotic-treated glycolysing cells experience passive K⁺ outflow down the concentrational gradient. It was thus concluded that the electrical potential cannot be the driving force for the energy-linked K⁺ transport in glycolysing cells.