Structure, morphology and crystal growth of bacterial magnetite

• Published in: Nature (London) 1984-01, Vol.310 (5976), p.405-407
• Main Authors: Mann, Stephen, Frankel, Richard B., Blakemore, Richard P.
• Format: Article
• Language: English
• Subjects: Earth sciences; Earth, ocean, space; Exact sciences and technology; Humanities and Social Sciences; letter; Mineralogy; multidisciplinary; Non silicates; Science; Science (multidisciplinary)
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/310405a0

Recent high-resolution transmission electron microscopy (HRTEM) studies of the structure and morphology of bacterial magnetite (Fe 3 O 4 ) crystals isolated from a magnetotactic coccus 1 and from an unidentified bacterium extracted from sediment 2 have shown the crystals to be well ordered single-domain particles with a morphology based on a hexagonal prism of {011} faces truncated by specific low index planes. We report here a HRTEM study of intact magnetite crystals (magnetosomes) in the microaerophilic bacterium Aquaspirillum magnetotacticum , grown in pure culture 3,4 . Our aim has been to investigate the structure, morphology and crystal growth of the magnetite particles in the light of a recent Mossbauer spectroscopy study of this organism 5 which indicated, in addition to magnetite, the presence of hydrated iron( III ) oxide phases together with the magnetosomes. Our results show that the mature particles are well ordered single-domain crystals of magnetite with a morphology very different from previously studied crystals and based on an octahedral prism of {111} faces truncated by {100} faces. We also show the first direct evidence for both crystalline and non-crystalline phases within individual magnetosomes. The results are important in aiding elucidation of the crystal growth mechanisms of biogenic magnetite.