Research internship or Master thesis


Magnetotactic bacteria biomineralize magnetite (Fe₃O₄) crystals enclosed in ca. 50 nm large membrane vesicles inside their cell bodies. These vesicles, called magnetosomes, invaginate from the cytoplasmic membrane of the bacterial envelope and arrange in a form of chains in the cytoplasm. The magnetic dipole moment of the magnetosome chain is sufficient to align the cell with the Earth magnetic field while swimming. From knock-out studies, several proteins associated with the vesicle membrane have been identified as necessary for magnetite biomineralization, but how these interact and coordinate the process remains poorly understood. Some of the proteins are transmembrane proteins, complicating biochemical protocols of their isolation and purification. Isolation of transmembrane proteins is a difficult experimental step due to a loss of the protein structure and activity after its removal form a native lipid environment. Therefore, biophysical approaches aiming at studies of lipid-protein environment are required and will be implemented here.

 

In this work, vesicles at different stages of mineralization will be investigated by means of electrochemistry, infrared and Raman spectroscopies. The membrane vesicles with different amounts of accumulated magnetite will be isolated in the Winklhofer group. Vesicles have an ability to spread into planar lipid membranes on solid surfaces. A lipid-protein membrane will be deposited on a gold electrode surface. Spreading of the membrane will be investigated using electrochemical techniques. To confirm the presence of the lipids and proteins in a film deposited in a gold surface, Infrared spectroscopy (IRS) and Surface Enhanced Raman Spectroscopy and Microscopy will be applied. Lipid and proteins possess functional groups which give vibrational modes at different wavenumbers, allowing for identification of both compounds. IRS and SERS will be used to identify the biomolecules and analyze the structural elements in proteins present in the membrane. This step will allow for identification of possible proteins originally accumulated in the vesicles. Magnetite gives Raman signals in the 1000 – 500 cm^-1 spectral region which are separated from the signals of lipids (ca. 3000 cm^-1) and proteins (1700 -1500 cm^-1). Raman imaging experiments will be used to map the surface and identify regions of the supported membrane that are rich in magnetite, proteins and lipids. It aims at identification of biomolecules responsible for the attachment and growth of magnetite in the vesicles.

 

This experimental work is part of collaboration project for the establishment of the NaviSence Cluster of Excellence at the University of Oldenburg.

 

 

Supervision: PD Dr. Izabella Brand

Cooperation: Prof. Dr. M. Winklhofer

 

 

Experimental biomimetic studies of lipid-protein-megnetite vesicles. Experimental work includes electrochemistry, IRS and RS experiments