Metabolic Characterisation of Magnetospirillum Gryphiswaldense MSR-1 Using LC-MS-Based Metabolite Profiling
<p>Magnetosomes are nano-sized magnetic nanoparticles with exquisite properties that can be used in a wide range of healthcare and biotechnological applications. They are biosynthesised by magnetotactic bacteria (MTB) such as <i>Magnetospirillum gryphiswaldense </i>MSR-1 (<i>Mgryph</i>). However, magnetosome bioprocessing yields low quantities compared to chemical synthesis of magnetic nanoparticles. Therefore, the understanding of the intracellular metabolites and the metabolic networks related to <i>Mgryph</i> growth and magnetosome formation are vital to unlock the potential of this organism to develop improved bioprocesses. In this work, we investigated the metabolism of <i>Mgryph</i> using untargeted metabolomics. Liquid chromatography-mass spectrometry (LC-MS) was performed to profile spent medium samples of <i>Mgryph </i>cells grown under O<sub>2</sub>-limited (n=6) and O<sub>2</sub>-rich conditions (n=6) corresponding to magnetosome- and non-magnetosome producing cells, respectively. Cross-validated multivariate, univariate and pathway enrichment analyses were conducted to identify significantly altered metabolites and pathways. Rigorous metabolite identification was carried out using authentic standards, <i>Mgryph-</i>specific metabolite database<i> </i>and<i> </i>MS/MS mzCloud database. PCA and OPLS-DA showed clear separation and clustering of sample groups with cross-validation values of R<sup>2</sup>X=0.76, R<sup>2</sup>Y=0.99 and Q<sup>2</sup>=0.98 in OPLS-DA. As a result, 50 metabolites linked to 45 metabolic pathways were found significantly altered in the tested conditions including glycine, serine and threonine; butanoate; alanine, aspartate and glutamate metabolism; aminoacyl-tRNA biosynthesis and; pyruvate and citric acid cycle (TCA) metabolisms. Our findings demonstrate the potential of LC-MS to characterise key metabolites in <i>Mgryph</i> and will contribute to further understand the metabolic mechanisms that affect <i>Mgryph</i> growth and magnetosome formation. <i></i></p>