Researchers have long-studied magnetotactic bacteria (MTB): aquatic microbes that have the ability to orientate themselves to magnetic fields. This unusual behaviour makes them a subject of interest for improving the understanding of biomagnetism, and potentially harnessing their abilities for future technologies, such as medical nanorobots.
Magnetotactic bacteria exert their magnetic navigation skills using magnetosomes – membrane structures containing magnetic nanoparticles that the bacteria mineralise from their environment. The magnetosomes arrange in a chain that acts like a magnetic compass. These unusual nanoparticles have been examined with neutron beams to discover the underlying mechanisms that determine the arrangement and geometry of the chains.
An international collaboration of researchers has elucidated the precise structural configuration of the magnetosomes in the MTB strain Magnetospirillum gryphiswaldense (pictured). They carried out small-angle neutron scattering (SANS) on a colloid of MTB, a technique that allows them to see the magnetic microstructure of the organisms in detail in aqueous solution.
Magnetic nanoparticles are central to many applications, ranging from biomedical diagnostics to data storage and even hyperthermia cancer treatments, but the magnetic structures within and between nanoparticles are challenging to probe directly. Neutron-spin resolved (or ‘polarised’) small-angle neutron scattering is one of the few tools that can be used to investigate nanoparticles in the relevant scale.
These findings, published in the journal Nanoscale, facilitate a better understanding of how the chain behaviour might affect applications of MTB. They could guide the development of biological nanorobots, which may deliver drugs or perform minor surgery inside the body.