1 bacterial cell takes up a photosensitizer,
2 optical radiation makes the photosensitizer generate active oxygen,
3 external radiation produces oxidant stress, which activates bacterial superoxide dismutase or simulates the synthesis of thermal-shock proteins; depending on the bacterial ability to "protect itself," the oxidant stress may cause:
4 death,
5 alteration in the bacterial envelope followed by changes in the bacterial resistance to microbicide compounds, or
6 inhibition of colony growth