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. New research by Pamela Silver and her colleagues takes us a step forward in understanding these processes by making yeast magnetic and then studying how this magnetization is regulated.
This 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 yeast – an otherwise non-magnetic organism – magnetic. 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 iron to cellular storage containers called vacuoles; the researchers deleted the gene for this transporter to prevent this from happening, thus allowing iron to accumulate in the yeast cells. The yeast were magnetized by adding genes to increase their ability to sequester iron and by mutating other genes to increase their magnetic properties by altering their metabolism. Although yeast with just the iron transporter deleted became magnetic, yeast that express the human ferritin gene in combination with this deletion displayed stronger magnetism. This suggests that magnetization does not rely on magnetic properties in normal yeast cells, but shows that it can be induced by manipulating the existing iron transport system or by introducing iron sequestering genes. The researchers conducted further experiments to determine which signaling pathways contributed to the induced magnetization. They identified a gene that controls the reduction-oxidation conditions of a cell – reduction-oxidation referring to chemical reactions in which atoms transfer electrons between one another – and that also induced the formation of iron-containing particles and magnetization of the cells.
The wider impact of this study is that it shows how magnetization might be induced in other non-magnetic organisms. Even cells without intrinsic magnetic properties might become magnetized through changes to existing pathways of iron storage and by altering regulation of reduction-oxidation conditions. These findings open up many new potential avenues for research, including the examination of how magnetic particles function in neurodegenerative diseases. In addition, magnetization is contactless, remote, and permeable, so it is one potential way to generate interactions between cells that might be useful for both bioengineering and therapy, for example.