Superoxide is released from KR-E. coli upon orange light irradiation.

a, Ordinary light image (left) and fluorescence image (right) of a KR-E. coli suspension observed under a microscope. Bar, 10 m. b, The production of superoxide by the irradiation of KR-E. coli detected with nitroblue tetrazolium (NBT) in an agarose gel. The top panels demonstrate a change in the E. coli with KillerRed before and after irradiation. A magnified portion (right) of the agarose gel near the KR-E. coli containing central pool indicates a formazan precipitation due to the diffusion of superoxide from the pool. Bar, 5 mm. The bottom panels demonstrate change in the color of the E. coli without KillerRed expression before and after irradiation.