Magnetotactic bacteria are a group of prokaryotes that share the ability to align
with external magnetic fields, due to the presence within their cytoplasm of one or
several chains of nanometer-sized magnetic crystals called the magnetosomes. The
orientation of the chain within the cell is critical for magnetotaxis, which allows these
bacteria to swim along the geomagnetic field lines. To do so, the magnetic moment
and thus the chain need to lie parallel to the swimming direction which, for elongated
bacteria such as AMB-1, is roughly parallel to the long axis of the cell. In most
studies, the alignment between the magnetic moment and the cell axis is taken for
granted, however no precise measurement has been performed to confirm this. In this
thesis, experiments performed to test this assumption are presented, and the results
show that for most studied bacteria the alignment is not perfect. The effect on the
orientation distributions is discussed and accounted for in the analysis performed to
measure the magnetic moment of individual bacteria.
A second project presented in this thesis is focused on the biomineralization process in
AMB-1. Magnetotactic bacteria synthesize crystals characterized by a well-controlled
morphology and a high chemical purity, which makes them interesting for biomedical
applications. To study how these crystals are produced, we used scanning trans-
mission X-ray microscopy, and preliminary results show that this tool is suitable for
studying this complex process. The methods developed and improved during this MSc
to perform these experiments are presented, and the first results show an evolution
in the spectroscopy of the magnetosomes as they grow. / Thesis / Master of Science (MSc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/24113 |
| Date | January 2018 |
| Creators | Le Nagard, Lucas |
| Contributors | Fradin, Cécile, Hitchcock, Adam, Physics and Astronomy |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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