Collaborative Research: Biophysical Analysis of Magnetosome Development in Magnetotactic Bacteria Under Ambient Conditions

Harvard University, Cambridge MA

Investigators

Abstract

Central to the survival of many organisms is their ability to manipulate inorganic molecules into elaborate crystalline structures such as skeletons, teeth, and protective shells. This ubiquitous process of "biomineralization" depends on the precise action of specialized proteins within cells to form minerals where they are needed and prevent their accumulation in sensitive tissues. Although progress has been made, much is not understood about how biomineralization is realized inside of individual cells and which genes control the process. This collaborative project will address this challenge by applying recent advances in magnetic imaging technology to detailed studies of biomineralization in a simple and well-controlled biological system: the production of nanoscale magnetic particles within magnetotactic bacteria (MTB), and the use by MTB of chains of these particles (known as magnetosomes) for orientation and travel along the Earth's magnetic field lines (known as magnetotaxis). During this project, students and postdoctoral researchers will receive training in scientific practices at the interface of the physical and life sciences. In addition, the project may inform the development of improved materials with broad practical relevance, as products of biomineralization have superior properties compared to those currently engineered by humans. The scientific goals of this project are to study the molecular mechanisms governing biomineralization and the development of magnetic nanoparticles in MTB. The studies will employ a "diamond magnetic imager" that exploits a nanoscale layer of quantum sensors at the surface of a diamond chip, enabling imaging of magnetic field patterns from individual MTB in a population under ambient laboratory conditions, with better than 50 nanometer spatial resolution and greater than 1 millimeter field-of-view. The investigators will apply the diamond magnetic imager to studies of magnetic nanoparticle growth in various MTB species and biomineralization mutants. The project will open a new window onto the physical processes enabling magnetotaxis, including the transition of magnetic nanoparticles from a superparamagnetic to a stable single-domain magnetic state during magnetic nanoparticle growth, and the role of interactions between magnetic nanoparticles within individual MTB. Magnetic measurements on genetic mutants will provide biological insights into the genes controlling the biomineralization process. Observations will also be made of the dynamics of the magnetic nanoparticle chain during the cell division cycle, both through time series magnetic measurements on different MTB as well as magnetic imaging of individual living MTB.