Under normal conditions , bacterial phytochromes absorb light for signaling instead of fluorescence .
Phytochromes can be turned fluorescent after deleting some of the signaling parts by genetic means such as site - directed mutagenesis .
Under normal conditions , bacterial phytochromes absorb light for signaling instead of fluorescence , but they can be turned fluorescent after deleting some of the signaling parts by genetic means such as site - directed mutagenesis .