Blue-light irradiation reduces the expression of puf and puc operons of rhodobacter sphaeroides under semi-aerobic conditions

Northern hybridization indicated that cells grown in the light under semi-aerobic conditions contained few or no transcripts from both the puf and puc operons, whereas cells grown in the dark under semi-aerobic conditions had high levels of these transcripts. The action spectra for the inhibition of expression of the puf and puc operons by light under semi-aerobic conditions were examined between 400 nm and 880 nm. The spectra indicated that light at 450 nm had the most inhibitory effect on the expression of the puc operon and a somewhat lower inhibitory effect on the puf operon. These results suggest that, in Rhodobacter sphaeroides, an unidentified blue pigment(s) regulates the expression of the puf and puc operons under semi-aerobic conditions.