Abstract :
Magnetic bacteria synthesize intracellular particles of magnetite, which are aligned in chains and enveloped by a membrane. A new species of magnetic bacterium was recently isolated from aerobic sediment from a pond in Tokyo, and is capable of growing aerobically to high cell densities. This strain may therefore be grown easily in mass culture. In such large-scale cultures a stationary phase is reached after four to five days, with a final cell concentration of 2×109 cells/ml. The small size of the bacterial magnetic particles and the inhibition of aggregation by intact magnetosome membranes result in a large surface/volume ratio. When bacterial magnetic particles were prepared by ultrasonication, they were well dispersed in water. Phospholipids comprised 58% of the total lipid content, and phosphatidyl ethanolamine accounted for 50% of the total phos-pholipid content. A gene relating to bacterial magnetic particles was cloned in Escherichia coli and analyzed. A system for magnetic bacteria gene cloning was also developed.
