Regulation mechanism of photopigments biosynthesis via light and oxygen in Rhodobacter azotoformans 134K20

Abstract:

Abstract: [Objective] To provided a reliable and sensitive method and a series of specific absorption spectra data of different carotenoids and bacteriochlorophylla in anxoygenic phototrophic bacteria, and reveal mechanism of regulation of photosynthetic pigments by light and oxygen in Rhodobacter azotoformans 134K20. [Methods] The metabolic diversity of photopigments regulated by oxygen and light was investigated by means of UV-VIS spectra and thin layer chromatography. [Results] The highest cell yield of strain 134K20 was obtained under aerobic conditions in the light. Nine types of photopigments including three yellow pigments, one red pigment, one purple pigment, two green pigments, and two blue pigments were synthesized, and yellow pigments synthetic genes were expressed on the higher level anaerobically in the light. Under aerobic conditions, the synthetic genes of two new red and one new purple pigment were triggered and expressed on the higher level, but the biosynthesis of yellow, blue and green pigments were inhibited by oxygen, another nine pigments including two yellow pigments, three red pigments, two purple pigments, one green pigment, and one blue pigment were synthesized. One yellow pigment was only produced in dark aerobic culture, the other pigments were the same as in dark aerobic cultures. [Conclusion] PpsR photopigment suppression regulation system regulated expression of photosynthetic genes via light and oxygen in Rhodobacter azotoformans 134K20. The yellow and red pigments belong to carotenoid series. The first yellow pigment belongs to spheroidene series. The other two yellow pigments are new carotenoids. Yellow pigments are capable of dissolving in different organic solvents. Red pigments belong to new spheroidenone series. The three red pigments are different in polarity, peak shape and peak value. Fine structures of red pigments only are appeared in hexane. The purple pigmments with polarity are identified as bacteriopheophytins. The blue and green pigments are four kinds of bacteriochlorophyll a intermediates. Diethylether and methanol is suitable for carotenoids extraction. The identification of bacteriochlorophyll a intermediates can be easily performed by polarity analysis.