The ability to detect and respond to magnetic fields is not usually associated with living things. Yet some organisms, including some bacteria and various migratory animals, do respond to magnetic fields. In migratory animals like fish, birds, and turtles, this behavior involves small magnetic particles in the nervous system. However, how these particles form and what they are actually doing is not fully understood.
In a new study, published February 28 in the online, open-access journal PLoS Biology, Keiji Nishida and Pamela Silver of Harvard Medical School take a major step forward in understanding these processes by making yeast magnetic and then studying how this magnetization is regulated.
Dr. Silver's lab uses 'synthetic biology' to generate organisms that do things that they don't usually do; for example, manipulating bacteria to produce fuel. In this paper, they make yeastan otherwise non-magnetic organismmagnetic.
"Magnetism exists throughout nature," explained Dr. Silver. "In particular there are magnetic bacteria and we wonder how these might have evolved." In addition, human nerve cells may also contain magnetic particles; iron deposits are seen in neurological disorders such as Alzheimer's. Yeast are a simpler system and more readily amenable to genetic manipulation, so making them magnetic also offered the opportunity to investigate the requirements for magnetization and how it is regulatedwhich not only provides significant new insights into how magnetization functions and is regulated in this system, but might also offer insights into how these particles form and what they are doing in diseases like Alzheimer's.
The researchers induced magnetization by first adding iron to the yeast cells' growth medium and then introducing the human ferritin proteins, which form a shell around iron and prevent it from being stored elsewhere in the cell. Ordinarily, yeast cells use an iron transporter to move excess i
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