Killing of Escherichia coli by Exogenous Hydroxyl Radicals

The effects and mechanisms were studied on killing of Escherichia coli, a Gram negative bacterium by exogenous hydroxyl radical. The results showed that, exogenous OH• was efficient on killing of E. coli cells. Over 99% of them was killed in 0.5 mg/L OH• solution. And exogenous OH• could damage biomolecules of E. coli. The concentrations and integrities of DNA, RNA and intracellular protein decreased with the increasing of the concentration of OH•, and the degree of decreasing of intracellular soluble protein concentration was higher than that of DNA or RNA. This indicated that protein is the major target of OH• among biomolecules in the cell. After treated by OH•, the leakage of electrolytes from cells increased. In 0.5 mg/L OH• solution, the value of relative leakage reached to 16.21%, which might be severe and fatal to E. coli cell. It was speculated that cell membrane is the initial target of exogenous hydroxyl radical.