Figure 1.
Biochemical pathways of oxidative and nitrosative species production within host or bacterial cells. Molecular oxygen is reduced to superoxide within innate immune cells by NADPH oxidase or produced inadvertently by complexes of the respiratory electron transport chain. Within neutrophils and inflammatory monocytes, H2O2 formed by dismutation of O2•− is converted to toxic HOCl by myeloperoxidase. Generation of the powerful oxidising species, the hydroxyl radical, is produced by the Fenton chemistry within the host and/or bacterial cells. Macrophages produce nitric oxide via NO synthase, which can interact with superoxide to produce peroxynitrite. Autoxidation of NO produces N2O3 and subsequent downstream reactions generate nitrogen dioxide radicals. The generation of ROS and RNS plays an important role in antibacterial defence by damaging important Campylobacter and Helicobacter cellular molecules.