Characterization of carotenoids in Rhodothermus marinus

Abstract

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 4252T, 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. marinus DSM 4252T genome was identified and analyzed, in which several genes were matched with carotenoid biosynthetic pathway genes in other organisms.

Composition analysis and minimal treatments to solubilize polysaccharides from the brown seaweed Laminaria digitata for microbial growth of thermophiles

“…These two bacterial strains produce metabolites with application potential and finding a sustainable growth source is thus of interest for their potential as cell factories utilizing seaweed-based feedstocks. R. marinus can produce carotenoids and exopolysaccharides (Sardari et al 2017;Ron et al 2018), while B. methanolicus strains are potential producers of cadaverine, γ-aminobutyric acid (GABA) and amino acids (Brautaset et al 2010;Irla et al 2014;Naerdal et al 2015).…”

“…The two bacterial species selected for this study represent highly different, but complementing, highly relevant substrate utilization profiles for the feedstock, and also both microbes produce products of interest. R. marinus has the capacity to produce exopolysaccharides (Sardari et al 2017) and carotenoids (Ron et al 2018) and for example B. methanolicus has been shown to produce cadaverine (Naerdal et al 2015).…”

Global Transcriptomic Responses of Roseithermus sacchariphilus Strain RA in Media Supplemented with Beechwood Xylan

“…Based on the list of CAZymes genes and the activities of the marker enzymes, strain RA is not a good degrader of plant biomass compared to that of other microorganisms in the hot spring. Furthermore, the performance of strain RA may be relatively low compared to the close relatives Rhodothermus marinus (DSM 4252) and Rhodothermus marinus SG0.5JP17-172 [24][25][26][27][28][29]. Nevertheless, strain RA had enhanced enzymatic activities, showed better growth, and higher transcriptomic responses toward xylan as the carbon source.…”

“…These enzymes act synergistically to achieve the complete degradation of cellulose. Endoglucanases, or also known as endo-1,4-β-d-glucanases (EC 3.2.1.4), are classified in GH 5,6,7,8,9,10,12,26,44,45,48,51,74, and 124 [8]. Endoglucanases initiate the cellulose hydrolysis process by acting on an amorphous region of the cellulose and yield cellodextrins with different lengths [10].…”

“…Members of Rhodothermaceae are halothermophile. Rhodothermus is well understood from the aspects of phenotypic, chemotypic, genomic and extrachromosomal elements, pathway and gene manipulations, environmental adaptation, as well as the discovery of industrial enzymes [23][24][25][26][27]. Bacteria strains such as Rhodothermus marinus (DSM 4252) and R. marinus SG0.5JP17-172 are excellent plant biomass degraders [28,29].…”