ROS-mediated killing efficiency with visible light of bacteria carrying different red fluorochrome proteins

Red fluorescent proteins can generate reactive oxygen species (ROS) if their fluorochrome is stimulated e.g. by visible light illumination. ROS compounds have very reactive, highly toxic properties leading to cell damage which results in cell killing. In this context, the toxicity of the various red fluorochromes KillerRed, DsRed2, mCherry, and mRFP expressed in Escherichia coli bacteria was tested after illumination with white light. The toxic effect was determined by measurement of the colony forming ability 24 h after transfection and illumination. KillerRed was found to be the most harmful, followed by mRFP and DsRed2 while bacteria expressing mCherry and controls without fluorescent proteins survived after application of identical illumination doses. Their application and a possible bactericide role is discussed.