The S pole distribution on magnetic grains in pyroxenite determined by magnetotactic bacteria

Minoru Funaki*, Hideo Sakai, Tadashi Matsunaga, Shigehisa Hirose


研究成果: Article査読

11 被引用数 (Scopus)


North-seeking bacteria (NSB) with 1 μm diameters migrate to the S pole only. They were applied to identify the S pole determination on a polished surface of magnetite-rich pyroxenite whose natural remanent magnetization (NRM) intensity was 5.64 × 10-3 Am2 kg-1. The microscopic observations were performed under dark-field illumination in a controlled magnetic field to 10 μT. The NSB formed clusters on limited areas of magnetite grains and scattered over the whole magnetite grains. The NRM decreased to 1.02 × 10-5 Am2 kg-1 by alternating field (AF) demagnetization to 60 mT but no clusters appeared, while small populations of the NSB scattered on each grain. These scattered bacteria may gather toward the S pole resulting from magnetic domain walls. When the sample acquired saturation isothermal remanent magnetization (SIRM) to 1 T, the NSB formed dense clusters at the opposite side to the applied field direction on the many grains as expected. This evidence indicated that the NSB can be useful micro-organisms for the determination of fine magnetic structures. Some grains also had NSB clusters at the edge of the grains toward the field direction or did not exhibit any clusters. The complicated distribution of the clusters (the S poles) may be explained by shape anisotropy of the magnetic grains.

ジャーナルPhysics of the Earth and Planetary Interiors
出版ステータスPublished - 1992

ASJC Scopus subject areas

  • 地球物理学
  • 宇宙惑星科学
  • 物理学および天文学(その他)
  • 天文学と天体物理学
  • 地球惑星科学一般
  • 環境科学一般


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