Abstract
BackgroundBecause of its tractability and straightforward cultivation, the magnetic bacterium Magnetospirillum gryphiswaldense has emerged as a model for the analysis of magnetosome biosynthesis and bioproduction. However, its future use as platform for synthetic biology and biotechnology will require methods for large-scale genome editing and streamlining.ResultsWe established an approach for combinatory genome reduction and generated a library of strains in which up to 16 regions including large gene clusters, mobile genetic elements and phage-related genes were sequentially removed, equivalent to ~ 227.6 kb and nearly 5.5% of the genome. Finally, the fragmented genomic magnetosome island was replaced by a compact cassette comprising all key magnetosome biosynthetic gene clusters. The prospective 'chassis' revealed wild type-like cell growth and magnetosome biosynthesis under optimal conditions, as well as slightly improved resilience and increased genetic stability.ConclusionWe provide first proof-of-principle for the feasibility of multiple genome reduction and large-scale engineering of magnetotactic bacteria. The library of deletions will be valuable for turning M. gryphiswaldense into a microbial cell factory for synthetic biology and production of magnetic nanoparticles.
Highlights
Because of its tractability and straightforward cultivation, the magnetic bacterium Magnetospirillum gryphiswaldense has emerged as a model for the analysis of magnetosome biosynthesis and bioproduction
We provide a proof of concept for large-scale genome editing and improvement towards a future chassis [54], which may turn M. gryphiswaldense into a microbial cell factory for the synthetic biology and high-yield production of magnetic nanoparticles
The native biosynthetic gene clusters within the magnetosome island (MAI) plus multiple large portions of ’junk’ between and adjacent to them should be substituted by a compact cassette comprising all key genes for magnetosome biosynthesis
Summary
Because of its tractability and straightforward cultivation, the magnetic bacterium Magnetospirillum gryphiswaldense has emerged as a model for the analysis of magnetosome biosynthesis and bioproduction. Magnetosomes are membrane-enclosed organelles that are synthesized by various aquatic bacteria for their magnetotactic navigation in the Earth’s geomagnetic field [1, 2] Apart from their biological function as magnetic sensors, magnetosomes represent microbially synthesized magnetic nanoparticles (MNP) consisting of monocrystalline magnetite (Fe3O4) or greigite (Fe3S4). Because of their strictly controlled biomineralization, bacterial magnetosomes have exceptional properties, such as high chemical purity and crystallinity, strong magnetization, and uniform sizes and shapes, which are largely unknown from chemically synthesized MNP [3,4,5]. The bacteria were utilized as a model to study the molecular mechanisms of human diseases related to homologs of certain magnetosome proteins [23]
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