Evaluation of the Effects of Reactive Oxygen Species on Growth of Escherichia coli by Electron Spin Resonance Spin Trapping

Accumulation of reactive oxygen species (ROS) in the culture medium may inhibit the growth of microorganisms and prevent the detection of harmful bacteria in foods. In this study, we investigated the relationship between ROS (hydroxyl radical and hydrogen peroxide) and Escherichia coli growth using electron spin resonance, which detects and quantifies multiple oxygen free radicals simultaneously. ROS had little effect on the growth of normal E. coli cells. In contrast, heat-treated E. coli cells were sensitive to ROS, and the number of colony-forming units increased 10-fold with the addition of sodium thiosulfate or sodium pyruvate, both of which scavenge ROS in the culture medium. Both compounds efficiently scavenged hydroxyl radical, while sodium pyruvate eliminated hydrogen peroxide to a greater extent than sodium thiosulfate. Our results imply that hydroxyl radical levels are more critical for the growth and survival of damaged E. coli cells.