Investigating the presence and distribution of organic components in bacterial magnetite

The formation of magnetites within magnetosomes is subjected to highly controlled biomineralization processes by bacteria. Similar biominerals have been observed to contain occluded ("intra-crystalline") organics, revealing significant information about such processes. The size of magnetite particles produced by bacteria (< 100 nm) and limitations in analytical instrumentation have hindered a better understanding of whether organics are located within these nanoparticles. In this study, bright field TEM images, STEM images, and EDS chemical data have been collected for magnetite particles produced by Magnetospirillum gryphiswaldense in order to investigate the potential presence and distribution of organic components. Results reveal low atomic number features in STEM images, suggesting presence of an organic matrix near the edges of nanoparticles. Additionally, STEM-EDS analysis indicates presence of phosphorous within the magnetosome nanoparticles. The mean P/Fe ratio for the outer half of the magnetsome nanoparticles was significantly higher than the mean ratio for the inner "core", suggesting that phosphorus is present with greater magnitude in the "rim" in a co-location with STEM features. Phosphorus is not accounted for in any known mineral constituent of the samples and it is a vital organic element, present in certain types of lipids, which have been associated to the formation of magnetosomes. Overall results contribute to a better knowledge of these highly controlled biomagnetite particles, with significant implications for the recognition of biomarkers and their potential applications in nanotechnology and medicine.