Magnetotactic bacteria as a paleo-environmental proxy

　　Dr Thomas A. Berndt

　　北京大学

　　2020.05.28 （星期四）13:00

　　Zoom Meeting: https://zoom.us/j/99817666755  Meeting ID: 998 1766 6755

　　Abstract

　　Magnetosome chains produced by magnetotactic bacteria (MTB) are abundant magnetic minerals in sediments. They are not only excellent remanence recorders, but are also potentially important proxies for tracing environmental conditions. There is a wide variety of MTB species, each with their particular environmental preferences and with particular physical characteristics of the magnetic particles they synthesize. Moreover, it has also been observed that these physical characteristics may evolve in response to environmental conditions such as oxygenation, Iron availability, and organic carbon influx. Variations of magnetotactic bacteria abundances, species, and magnetosome morphology are therefore highly sensitive indicators of past environmental conditions. Contrary to many conventional paleo-environmental proxies, magnetosomes can easily be detected using fast and non-destructive experimental magnetic techniques. While these experimental techniques are efficient and well-established, current research focusses on establishing quantitative relationships between magnetic signals (in particular magnetic hysteresis loops) to the physical characteristics of the magnetosomes (morphology).

　　Recently, we used micromagnetic finite-element models to simulate such magnetic signals for a large variety of magnetosome morphologies. We systematically explored the parameter-space of magnetosome crystal size, elongation and intra-chain spacing. Additionally, we measured transmission electron microscopy (TEM) images of various magnetotactic bacteria to study correlations in these parameters that allow to quantify magnetosome morphology from simple hysteresis loops, and in turn showing a pathway to use magnetic measurements as a paleo-environmental proxy.

　　Biography of the Speaker

　　Dr. Thomas A. Berndt became an Assistant Professor of Peking University since 2019. He received BSc from University of Southampton in 2010, MSc from Universidad Complutense de Madrid in 2013, and PhD from Imperial College London in 2016.

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