[S-EM18] Geomagnetism, paleomagnetism and rock magnetism

[SEM18-12] Density separation and magnetic measurements of magnetotactic bacteria Magnetospirillum magnetotacticum MS-1

*Kohei Masaoka¹, Yuki Morono², Naotaka Tomioka², Go-Ichiro Uramoto¹, Yuhji Yamamoto¹ (1.Kochi University, 2.Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology)

Variation of the past geomagnetic field is recorded in marine sediments as a fossil magnetization, called natural remanent magnetization (NRM). NRM is carried not only by detrital and eaolian magnetic grains but also by biogenic magnetic grains originated from magnetotactic bacteria. To investigate characters of NRM carried by biogenic magnetic grains we have cultured the microaerobic bacteria Magnetospirillum magnetotacticum MS-1 (here under, MS-1) in laboratory and made sample using them for remanent magnetization measurements by simulating a very early process of sediment formation.

Preliminary reports on properties and characters of the remanent magnetization carried by the samples have been presented in Masaoka et al (2018JpGU; 2018SGEPSS), but MS-1 cells used for making samples rarely contain magnetite grains in these cells (3 percent of the total cells). To try to increase number of the cells containing magnetite grains, we have tested a density separation method using different density gradient centrifugation and made samples for magnetic measurements using these cells. We will report these results including observations under transmission electron microscope.