Division of Biotechnology, Department of Chemistry, Lund University, Lund, Sweden.
Division of Centre for Analysis and Synthesis, Department of Chemistry, Lund University, Lund, Sweden.
Microbiologyopen. 2018 Feb;7(1). doi: 10.1002/mbo3.536. Epub 2017 Oct 17.
Rhodothermus marinus, a marine aerobic thermophile, was first isolated from an intertidal hot spring in Iceland. In recent years, the R. marinus strain PRI 493 has been genetically modified, which opens up possibilities for targeted metabolic engineering of the species, such as of the carotenoid biosynthetic pathway. In this study, the carotenoids of the R. marinus type-strain DSM 4252 , strain DSM 4253, and strain PRI 493 were characterized. Bioreactor cultivations were used for pressurized liquid extraction and analyzed by ultra-high performance supercritical fluid chromatography with diode array and quadropole time-of-flight mass spectrometry detection (UHPSFC-DAD-QTOF/MS). Salinixanthin, a carotenoid originally found in Salinibacter ruber and previously detected in strain DSM 4253, was identified in all three R. marinus strains, both in the hydroxylated and nonhydroxylated form. Furthermore, an additional and structurally distinct carotenoid was detected in the three strains. MS/MS fragmentation implied that the mass difference between salinixanthin and the novel carotenoid structure corresponded to the absence of a 4-keto group on the ß-ionone ring. The study confirmed the lack of carotenoids for the strain SB-71 (ΔtrpBΔpurAcrtBI'::trpB) in which genes encoding two enzymes of the proposed pathway are partially deleted. Moreover, antioxidant capacity was detected in extracts of all the examined R. marinus strains and found to be 2-4 times lower for the knock-out strain SB-71. A gene cluster with 11 genes in two operons in the R. marinusDSM 4252 genome was identified and analyzed, in which several genes were matched with carotenoid biosynthetic pathway genes in other organisms.
海洋需氧嗜热菌 Rhodothermus marinus 最初是从冰岛的一个潮间温泉中分离出来的。近年来，R. marinus 菌株 PRI 493 经过基因改造，为该物种的靶向代谢工程开辟了可能性，例如类胡萝卜素生物合成途径。在这项研究中，对 R. marinus 标准菌株 DSM 4252、菌株 DSM 4253 和菌株 PRI 493 的类胡萝卜素进行了表征。使用生物反应器培养进行加压液相提取，并通过超高效超临界流体色谱与二极管阵列和四极杆飞行时间质谱检测（UHPSFC-DAD-QTOF/MS）进行分析。Salinixanthin 是一种最初在 Salinibacter ruber 中发现的类胡萝卜素，以前在菌株 DSM 4253 中检测到，在所有三种 R. marinus 菌株中均以羟基化和非羟基化形式存在。此外，在这三种菌株中还检测到了另一种结构不同的类胡萝卜素。MS/MS 碎片暗示 salinixanthin 和新型类胡萝卜素结构之间的质量差异对应于β-紫罗兰酮环上缺少 4-酮基团。该研究证实了缺乏基因编码途径中两个酶的部分缺失菌株 SB-71（ΔtrpBΔpurAcrtBI'::trpB）的类胡萝卜素。此外，还检测到所有被检查的 R. marinus 菌株的提取物中的抗氧化能力，并且发现缺失菌株 SB-71 的抗氧化能力低 2-4 倍。在 R. marinusDSM 4252 基因组中，鉴定并分析了两个操纵子中的 11 个基因的基因簇，其中一些基因与其他生物体中的类胡萝卜素生物合成途径基因匹配。
