Magnetospirillum gryphiswaldense MSR-1 can biomineralize the magnetosome, nanoscale magnetite (Fe₃O₄) surrounded by a lipid bilayer, inside the cell. The magnetosome chain(s) enables MSR-1 to move along with the magnetic field (magnetoaerotaxis). Due to its unique characteristics, MSR-1 has attracted attention for biotechnological applications. During cultivation, not only the optical density but also the magnetosome content in MSR-1 should be monitored. The ferrozine assay had been utilized to quantify the iron content in magnetosomes. However, the effectiveness of the ferrozine assay on iron oxide nanoparticles is still unknown. Here, we examined the experimental factors, and the amended ferrozine assay demonstrates a recovery of 88.71% for Fe₂O₃ nanoparticles relative to the stock solution. Next, we apply the assay to analyze MSR-1 samples, which successfully reveals the difference in iron contents between magnetic and nonmagnetic MSR-1 samples and highlights the amount of MSR-1 cell density suitable for amended ferrozine assay. The assay further helps us examine the effects of centrifugation compared to magnetic separation (MS). The detection of residual magnetosomes in the supernatant indicates that MS remains a suitable method for collecting magnetosomes. We anticipate the amended ferrozine assay will facilitate research on MSR-1 by enabling investigators to measure iron content in cells in a fast, easy, and cost-effective manner.

中文翻译：

---

用于定量趋磁细菌中磁小体铁含量的改良 Ferrozine 测定法。


Magnetospirillum gryphiswaldenseMSR-1 可以在细胞内生物矿化被脂质双层包围的磁小体纳米级磁铁矿 （Fe₃O₄）。磁小体链使 MSR-1 能够随磁场移动（趋磁性）。由于其独特的特性，MSR-1 在生物技术应用中引起了人们的关注。在培养过程中，不仅应监测光密度，还应监测 MSR-1 中的磁小体含量。铁嗪测定法已用于量化磁小体中的铁含量。然而，铁嗪测定对氧化铁纳米颗粒的有效性仍然未知。在这里，我们检查了实验因素，修正的 ferrozine 测定表明，相对于储备溶液，Fe₂O₃ 纳米颗粒的回收率为 88.71%。接下来，我们应用该测定法分析 MSR-1 样品，成功揭示了磁性和非磁性 MSR-1 样品之间铁含量的差异，并突出了适合改良铁嗪测定的 MSR-1 细胞密度。该分析进一步帮助我们检查离心与磁性分离 （MS） 相比的效果。检测上清液中的残余磁小体表明 MS 仍然是收集磁小体的合适方法。我们预计修改后的 ferrozine 测定将使研究人员能够以快速、简单且经济高效的方式测量细胞中的铁含量，从而促进 MSR-1 的研究。