Potentiometric Investigation of the Dynamics of Bacteriophage - Induced Potassium Ion Efflux in Escherichia coli

Abstract

Potassium is a very stable component of biological systems and contributes to maintaining positive turgor pressure of the cells. Although ion-selective electrodes (ISEs) have been used previously for measuring bacteriophage -induced potassium ion efflux in bacteria, the dynamics of this outcome remain unclear. In this study, the effects of incubation time, reaction volume, and phage/bacterial concentration on bacteriophage-induced potassium ion efflux were studied using a commercial ISE. A phage-bacteria reaction volume of 200 µl incubated at 37°C for 30 minutes was found to be optimal for detecting potassium ion efflux using the ISE. Potassium ion efflux was found to be directly proportional to phage multiplicity of infection and ~5 × 10 7 cfu/ml appeared to be the lowest bacterial concentration at which potassium ion efflux could be measured reliably. Furthermore, the differences in potassium ion efflux between control (bacteria + assay buffer) and test (bacteria + phage) samples were statistically significant (p < 0.05) and the results were consistent across assays performed on different days. The average of absolute concentrations of effluxed potassium ions was 1.4 mg/L for ~5 × 10 8 cfu/ml of bacteria (MOI (Multiplicity of infection) = 100). The method uses simple bench-top technology, has a rapid turnaround time, is label-free, and has the potential for incorporation in bacterial detection systems.