Abstract: The magnetic nanoparticles were extracted from Leptospirillum ferriphilum, strain YSK, isolated from acid mine drainages by treatment with sodium dodecyl sulfate(SDS) and centrifugation through a sucrose density gradient. Transmission electron microscopy(TEM) indicates that the nanoparticles are approximately spherical with a mean diameter of 44 nm, and magnetite crystals in this size range are single magnetic domains. Energy-dispersive X-ray analysis shows that the nanoparticles primarily contain two kinds of elements, iron and oxygen. Thus it can be concluded that the magnetic particles are magnetosomes. Generally, it is thought that cellular magnetotaxis is a direct consequence of the cell possessing magnetosomes. The discovery of magnetosomes in strain YSK can provide the theoretical basis for screening efficient bioleaching bacteria which are specific to different magnetic minerals under an outer magnetic field.

Key words: Leptospirillum ferriphilum; strain YSK; SDS; sucrose density gradient; magnetosomes; magnetotaxis