Investigation of biogenic magnetite particles by high-resolution electron microscope

In 1975, Blakemore found aquatic bacteria that swim along earth's magnetic lines of force [1]. They have permanent magnets of iron-rich fine particles within them. Such particles were found by Mössbauer analysis to consist of magnetite in the case of magnetospirilla [2]. In addition, Towe et al confirmed by electron diffraction that the particles were crystalline [3]. The purpose of the present investigation is to determine the crystal and magnetic structure of these particles by both high-resolution lattice imaging and electron holography; however only the former is reported here.Magnetotactic bacteria were gathered in a fresh-water pond. The specimens were peanut-shaped, and approximately 3um in length. Transmission electron micrographs, such as that shown in Fig. 1, reveal that approximately 30 fine particles are aligned within each bacterium.