Electron spectroscopic imaging of magnetotactic bacteria: Magnetosome morphology and diversity

Magnetotactic bacteria from aquatic environments were analyzed with the ele ctron spectroscopic imaging technique. Rod-shaped bacteria and cocci were p resent in most of the samples observed. Magnetotactic multicellular aggrega tes were also observed at some of the sampling sites. The use of electron s pectroscopic imaging allowed the observation of magnetosomes inside magneto tactic microorganisms with exceptional clarity. The number, size, and morph ology of magnetosomes, as well as their ultrastructural spatial disposition inside the bacterial cell, could be directly observed and associated with the disposition of flagella of the respective cells. This allowed us to exa mine the structural relationships between magnetosomes and flagella, which are important components in the mechanisms of magnetotaxis. In disrupted ma gnetotactic multicellular aggregates, connections between cells were also v isualized. We believe this technique will be useful in studying not only ma gnetotactic bacteria but also other uncultured microorganisms from natural environments.