CYBB and infection: We next tested if NOX2 enzymatic activity affects the ΔpH of intracellular Salmonella. Fluorescent microscopy showed that the cytoplasm of intracellular Salmonella reaches a pHi of ~5.6 by 30 min after infection of periodate-elicited peritoneal macrophages from C57BL/6 mice (Fig. 3h).