High‐Yield Production, Characterization, and Functionalization of Recombinant Magnetosomes in the Synthetic Bacterium Rhodospirillum rubrum “magneticum”

Abstract

Recently, the photosynthetic Rhodospirillum rubrum has been endowed with the ability of magnetosome biosynthesis by transfer and expression of biosynthetic gene clusters from the magnetotactic bacterium Magnetospirillum gryphiswaldense. However, the growth conditions for efficient magnetite biomineralization in the synthetic R. rubrum “magneticum”, as well as the particles themselves (i.e., structure and composition), have so far not been fully characterized. In this study, different cultivation strategies, particularly the influence of temperature and light intensity, are systematically investigated to achieve optimal magnetosome biosynthesis. Reduced temperatures ≤16 °C and gradual increase in light intensities favor magnetite biomineralization at high rates, suggesting that magnetosome formation might utilize cellular processes, cofactors, and/or pathways that are linked to photosynthetic growth. Magnetosome yields of up to 13.6 mg magnetite per liter cell culture are obtained upon photoheterotrophic large‐scale cultivation. Furthermore, it is shown that even more complex, i.e., oligomeric, catalytically active functional moieties like enzyme proteins can be efficiently expressed on the magnetosome surface, thereby enabling the in vivo functionalization by genetic engineering. In summary, it is demonstrated that the synthetic R. rubrum “magneticum” is a suitable host for high‐yield magnetosome biosynthesis and the sustainable production of genetically engineered, bioconjugated magnetosomes.

Exploring the host range for genetic transfer of magnetic organelle biosynthesis

“…Noteworthy, all but one transgenic strain found capable of magnetosome biosynthesis in this study grow preferably photoheterotrophically under anaerobic conditions, and this growth regime apparently stimulated magnetosome formation in comparison to microoxic chemotrophic cultivation as also demonstrated previously for R. rubrum 25,31 . The strains synthesizing more numerous magnetosomes, e.g., Rm.…”

“…Therefore, we first screened all the Mag+ and Mag-hosts, including the previously reported 19,20,43 , for the presence of AUGs (see Materials and Methods for details). Of 90 AUGs, predicted in the previous studies, only 25 were found present in the genomes of all Mag+ (in the following, filtered auxiliary genes, FAGs). However, among FAGs there were none that would be absent in ALL Mag-, suggesting that the lack of the desired phenotype in them cannot be simply attributed to the universal absence of a certain gene(s) from the currently known AUGs set (Fig.…”

“…These findings have stimulated enormous efforts within the synthetic biology community to transfer magnetosome biosynthesis into more facile hosts, and even inspired ideas to borrow genetic parts from MTB for endogenous magnetization of cells from higher organisms [21][22][23] . Heterologous magnetosome biosynthesis in other, biotechnologically relevant and more tractable hosts would also alleviate some problems associated with the challenging cultivation and limited tractability of the available native and synthetic magnetic bacterial strains 24,25 . However, despite the encouraging results, simple transfer of magnetosome genes has failed for several other potential hosts.…”

The Roles of Optogenetics and Technology in Neurobiology: A Review

“…Nowadays, optogenetic can be used to treat eye diseases such as color blindness ( Table 1 and Figure 3 ; Cideciyan et al, 2016 ). The researchers sensitized the cells to light by the expression of light genes that encode light-activated channels or pumps in the remaining retinal cells ( Ostrovsky and Kirpichnikov, 2019 ; Blomeier et al, 2021 ; He et al, 2021 ; Kramer et al, 2021 ; Mickoleit et al, 2021 ). Relevant research has achieved good results in recent years.…”

Emerging enzyme surface display systems for waste resource recovery

“…Functionalized magnetosomes can be engineered by inserting proteins or peptides into magnetosome membrane proteins (Figure 3 ) (Mickoleit & Schüler, 2018 ). Interestingly, magnetosome gene clusters can now be transferred to non‐magnetic bacteria enabling efficient magnetosome cultivation (Kolinko et al, 2014 ; Mickoleit et al, 2021 ), and rapid, continuous systems for magnetosome purification have been developed to increase scalability using reversible magnetic fields (Guo et al, 2011 ; Zwiener et al, 2021 ).…”