Annual Review 2024-2025

D I A M O N D L I G H T S O U R C E L I M I T E D 11 CryoSXT is a powerful technique used to observe the internal structure of biological samples in a near-native state. In this study, it was instrumental in providing three-dimensional (3D) tomograms of individual bacterial cells. The technique allowed for high-resolution imaging without the need for traditional sample preparation that could damage cellular structures. On B24, the team was able to observe internal compartment including magnetosomes using the preferential absorption of carbon atoms in the cell. With cryoSIM, they stained the cell with PG-SK, a green fluorophore that reacts with the intracellular iron. The strength of the B24 beamline is that scientists were able to analyse the same region of interest in the same samples with Both CryoSIM and CryoSXT and correlate the data. This approach provided compelling evidence of a correlation between the intracellular iron concentration and the number of magnetosomes. By modifying the oxygen concentration during the bacteria growth, the researchers demonstrated that these bacteria can tolerate high extracellular iron concentrations. Understanding how magnetotactic bacteria and magnetosomes grow is essential as there is a growing interest into using magnetosomes for biotechnological and biomedical applications due to their unique properties such as narrow iron distribution and biocompatibility. DOI: 10.1021/acsami.4c15975 B I O L O G I C A L C R Y O - I M A G I N G G R O U P Representative tomogram slices of the MSR-1 magnetosome producing cell grown under microaerobic conditions imaged by cryoSIM and cryoSXT, including a 3D volumetric representation of this cell using a SuRVos2 workbench. Magnetosomes are coloured in pink, PHA granules in blue and the cell membrane in purple. In the cryoSIM image, the intracellular iron is indicated by the Phen Green SK fluorophore (PG-SK) CryoSIM Overlay 3D Volume CryoSXT Overlay 3D Volume 2um 2um 2um 2um