Towards a 'chassis' for bacterial magnetosome biosynthesis: genome streamlining of Magnetospirillum gryphiswaldense by multiple deletions

Background: 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. However, its future use as platform for synthetic biology and biotechnology will require methods for large-scale genome editing and streamlining. Results: We 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 similar 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. Conclusion: We 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.

Automated summary

The study established an approach for combinatory genome reduction in Magnetospirillum gryphiswaldense, resulting in a library of strains with multiple regions removed. A compact cassette comprising key magnetosome biosynthetic gene clusters replaced the fragmented genomic magnetosome island, showing wild type-like cell growth and magnetosome biosynthesis under optimal conditions, as well as improved resilience and genetic stability. This proof-of-principle for multiple genome reduction and large-scale engineering of magnetotactic bacteria will be valuable for synthetic biology and nanoparticle production.