铁对产铁载体的沼泽红假单胞菌光合色素与铁载体合成的影响

Influence of iron on siderophore and photosynthetic pigments biosynthesis by siderophore-producing Rhodopesudomonnas palustris

【目的】探求铁对1株能产生铁载体的不产氧光合细菌(Anoxygenic Phototrophic Bacteria,APB)光合色素和铁载体合成的影响。【方法】通用CAS法检测铁载体产生,Arnow、Csaky和Shenker法检测铁载体类型;吸收光谱法和HPLC法分析光合色素的组分和含量。【结果】Rhodopseudomonas palustris CQV97能够产生异羟肟酸型铁载体,未添加FeCl3时,铁载体含量最高,铁载体的产生与生长并非关联型。随FeCl3浓度升高,菌体生长潜伏期缩短,生长速率、最终生物量以及细菌叶绿素(Bacteriochlorophyll,BChl)a和类胡萝卜素(Carotenoid,Car)含量均提高,而检测到的游离铁载体含量降低;菌体积累的BChl a的组成和相对含量未见明显变化,但主要的Car组分由Spirilloxanthin转化为Rhodopin,菌体中积累Car组分的平均共轭体系降低,Car组成的改变与色素提取液的Car特征性光谱蓝移现象相吻合。【结论】首次报道APB能够产生铁载体,CQV97菌株能够产生异羟肟酸型铁载体。阐明了铁对CQV97生长、铁载体产生和光合色素合成的影响规律,这些研究结果为深入开展APB铁载体分离纯化以及生物功能研究奠定了基础。

[ Objective ] To explore the regulation of iron on siderophore production, cell growth and photosynthetic pigments biosynthesis by siderophore-producing anoxygenic phototrophic bacteria. [ Methods] Siderophore production was determined using Chrome Azurol S （CAS） assay. The siderophore types were determined by Arnow method, Csaky test and Shenker test. The compositions and contents of photosynthetic pigments were determined by spectrophotometry and HPLC analysis. [Results] Rhodopseudomonas palustris （Rps. palustris） CQV97 was capable of producing hydroxamatetype of siderophore. Siderophore production reached the highest yield in the absence of ferric chloride. With increasing ferric chloride concentrations, the lag phase of cell growth was shortened, and the cell growth rate, final biomass and the total amounts of carotenoid and bacteriochlorophyll a were increased significantly. The characteristic absorption maxima of carotenoids from pigment extracts were blueshifted. Iron concentration had little effect on the compositions and relative contents of bacteriochlorophylls a, whereas predominately affected carotenoid compositions, rhodopin was present as major carotenoid component instead of spirillxanthin. Culture tends to accumulate the Cars having shorter conjugated double bonds at the expense of longer conjugated double bonds as the ferric chloride concentration increased. The changes in carotenoid composition were consistent with those of the blue shift of absorption spectra of pigment extracts. [ Conclusion ] Rps. palustris CQV97 can produce siderophore and the changes in microbial growth, siderophore production and photosynthetic pigments accumulation of anoxygenic phototrophic bacteria are related to the iron concentration in the medium.