A-NO2−-mediated killing of S aureus USA300 under anaerobic conditions. NaNO2 concentrations tested were 0 μg ml−1 (closed circles), 512 μg ml−1 (open circles), 1,024 μg ml−1 (squares), and 2,048 μg ml−1 (triangles). The graphs represent the averages of three independent cultures analyzed concurrently.