Understanding Magnetosome Formation and Organization using Scanning Transmission X-ray Microscopy – X-ray Magnetic Circular Dichroism

Abstract

<p>Magnetotactic bacteria (MTB) are ubiquitous, multi-phylogenetic bacteria that actively synthesize chains of magnetic, membrane bound; single domain magnetite (Fe₃O₄) or greigite (Fe₃S₄) crystals, termed magnetosomes in order to better navigate to their preferred chemical environment using the Earth’s magnetic field. Discovered in 1963, the field is now focused on understanding magnetosome chain formation and associated processes through genetic studies as well as analytical techniques such as Transmission Electron Microscopy (TEM) and Scanning Transmission X-ray Microscopy – X-ray Magnetic Circular Dichroism (STXM-XMCD).</p> <p>This thesis performed studies on <em>Candidatus Magnetovibrio blakemorei</em> strain MV-1 using STXM at the C 1s, O 1s, Ca 2p and Fe 2p edges. STXM-XMCD was used to determine the magnetism of individual magnetosomes and quantitatively determine magnetic properties such as the magnetic moment of individual chains. A sub-population of MV-1 cells was identified as having anomalous magnetic orientations of magnetosome sub-chains when separated spatial gaps. The frequency of this event and the underlying implications to magnetosome formation are discussed.</p>