THE ROLE AND REGULATION OF HYDROXYL RADICALS AGAINST MICROBIAL PATHOGEN

Host immune systems generate reactive oxygen species (ROS) to defend microbial pathogens. ROS induce oxidative stress and they encompass nonradical oxidants, such as hydrogen peroxide and singlet oxygen and oxygen free radicals, such as superoxide anion radical and hydroxyl radical. Most aerobic metabolism cells is continuously produced them and their high toxicity could lead to cell death. Particularly, the Fenton reaction results in hydroxyl radical, which is highly toxic to the cell, causes double-stranded breaks in DNA, damage of protein and lipid. A common mechanism of fungicidal and bactericidal antibiotics involves the production of hydroxyl radicals. This mechanism depends on the metabolism of respiration including the electron transport chain and tricarboxylic acid (TCA) cycle. To protect oxidative damage in the cell, the level of hydroxyl radical is tightly regulated due to the enzymatic or non-enzymatic mechanism. This chapter is focused on the effect of hydroxyl radical and the regulation mechanism.