Synchrotron takes bearing on nano magnets
Scanning transmission X-ray microscope image of bacterial cells taken at the CLS. The blue dots are iron-containing magnetosomes, each about 30 billionths of a metre in size. Image courtesy of Adam Hitchcock, McMaster University.
Since the late 1960’s, scientists have known that some bacteria make internal compasses by growing tiny magnetic crystals called magnetosomes. The bacteria use them to navigate, positioning themselves in environments most suited for their survival, with cells of the same species growing crystals of uniform size, structure and out of the same magnetic minerals. Using the Canadian Light Source, researchers have for the first time been able to ‘see’ the magnetism of magnetosomes inside individual bacterial cells using the synchrotron’s X-ray microscope.
“We were surprised that we could do it at all,” remarks Adam Hitchcock, a professor at McMaster University’s Brockhouse Institute of Materials Research and principal investigator with the CLS’s X-ray Spectromicroscopy beamline. “But not only can we do it, we’ve now got a very powerful tool that can be used by groups doing research into how these magnetosomes form and how their structure could be manipulated.”
The finding sheds light on how magnetosomes grow in bacterial cells in response to genetic and environmental factors. Such understanding could be used by researchers to genetically manipulate the bacteria to grow magnetosomes that are tailor made for use in new kinds of data storage devices, nanomachines or delivery systems for cancer chemotherapy and other drug treatments. Such nanodevices could be moved and steered to the where they need to be – such as the site of a tumour or damaged tissue– using external magnetic fields.
Hitchcock and his team used the CLS Scanning Transmission X-ray Microscope (STXM) to probe the magnetic signal and crystal composition of individual magnetosomes about 30 billionths of a metre in size inside cultured bacterial cells. They found that, while largely similar to the mineral magnetite, the synchrotron’s X-ray microscope was able to detect small chemical variations from the bulk mineral as well as from one magnetosome to another, likely due to the chemical environment inside the bacteria where the magnetosomes grew.
Hitchcock is hopeful that with further work they will be able to measure these chemical differences in greater detail, making the STXM a valuable tool for studying how magnetosomes grow in the wild and how the process could be altered to build nanomagnets.
“People are already talking about the interplay between biology, magnetic materials and applications in areas such as medicine,” says Hitchcock. “Now we can look at different strains of bacteria that use different magnetic materials and start to understand how nature is doing this inside individual cells. It could lead to some really interesting stories.”
Reference: Lam, K.P., Hitchcock, A.P. et al. 2010. Characterizing magnetism of individual magnetosomes by X-ray magnetic circular dichroism in a scanning transmission X-ray microscope. Chemical Geology 270, pp. 110-116. DOI: 10.1016/j.chemgeo.2009.11.009
Last modified: 2012-01-19 17:01:42