不产氧光合细菌光合色素的光氧调控机制

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

摘要:

摘要: 【目的】为不产氧光合细菌光合色素研究提供可行的较系统规范的研究方法和数据，揭示固氮红细菌（Rhodobacter azotoformans 134K20）光合色素光氧适应性机制。【方法】采用光谱法和色谱法对光和氧调控下的类胡萝卜素和细菌叶绿素合成代谢进行了研究。【结果】134K20菌株光照好氧时细胞得率最高。光照厌氧时主要合成3黄、1红、1紫、2绿、2蓝9种色素，黄色素大量表达。有氧时红色素大量表达，且启动2种新的红色素和1种新的紫色素表达，而黄色和蓝绿色素则受氧抑制。黑暗好氧主要合成2黄、3红、2紫、1绿、1蓝9种色素，但不同于光照厌氧。光照好氧时黄色素减少到1种，紫色素含量增加，其余同黑暗好氧。【结论】 固氮红细菌（Rhodobacter azotoformans 134K20）是通过PpsR调节途径来调节光合基因表达的。黄色和红色素属于类胡萝卜素。黄色素1属于球形烯系列，其余两种黄色素是新的类胡萝卜素组分。红色素为新的球形烯酮组分，3种红色素极性、峰形和峰位差别显著，正己烷能显示其精细结构。紫色为极性较大的细菌脱镁叶绿素，绿色和蓝色为4种极性不同的细菌叶绿素a中间产物。乙醚甲醇法适合类胡萝卜素的提取，丙酮甲醇冰冻研磨法能快速有效完全提取光合色素。溶剂效应可有效鉴别细菌叶绿素a中间产物。

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.