title: Measuring spectroscopy and magnetism of extracted and intracellular magnetosomes using soft X-ray ptychography.
abstract: Characterizing the chemistry and magnetism of magnetotactic bacteria (MTB) is an important aspect of understanding the biomineralization mechanism and function of the chains of magnetosomes (Fe3O4nanoparticles) found in such species. Images and X-ray absorption spectra (XAS) of magnetosomes extracted from, and magnetosomes in, whole Magnetovibrio blakemorei strain MV-1 cells have been recorded using soft X-ray ptychography at the Fe 2p edge. A spatial resolution of 7 nm is demonstrated. Precursor-like and immature magnetosome phases in a whole MV-1 cell were visualized, and their Fe 2p spectra were measured. Based on these results, a model for the pathway of magnetosome biomineralization for MV-1 is proposed. Fe 2p X-ray magnetic circular dichroism (XMCD) spectra have been derived from ptychography image sequences recorded using left and right circular polarization. The shape of the XAS and XMCD signals in the ptychographic absorption spectra of both sample types is identical to the shape and signals measured with conventional bright-field scanning transmission X-ray microscope. A weaker and inverted XMCD signal was observed in the ptychographic phase spectra of the extracted magnetosomes. The XMCD ptychographic phase spectrum of the intracellular magnetosomes differed from the ptychographic phase spectrum of the extracted magnetosomes. These results demonstrate that spectro-ptychography offers a superior means of characterizing the chemical and magnetic properties of MTB at the individual magnetosome level.
authors.affiliation: Department of Chemistry and Chemical Biology, McMaster University, Hamilton, ON, Canada L8S 4M1.
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Zhu
authors.affiliation: Department of Chemistry and Chemical Biology, McMaster University, Hamilton, ON, Canada L8S 4M1; aph@mcmaster.ca.
authors.forename: Adam P
authors.initials: AP
authors.lastname: Hitchcock
authors.affiliation: School of Life Sciences, University of Nevada at Las Vegas, Las Vegas, NV 89154.
authors.forename: Dennis A
authors.initials: DA
authors.lastname: Bazylinski
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.
authors.forename: Peter
authors.initials: P
authors.lastname: Denes
authors.affiliation: Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.
authors.forename: John
authors.initials: J
authors.lastname: Joseph
authors.affiliation: Instituto de Microbiologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 2194-590, Brazil.
authors.forename: Ulysses
authors.initials: U
authors.lastname: Lins
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.
authors.forename: Stefano
authors.initials: S
authors.lastname: Marchesini
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.|National Synchrotron Radiation Research Center, Hsinchu, Taiwan 30076, Republic of China.
authors.forename: Hung-Wei
authors.initials: HW
authors.lastname: Shiu
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.
authors.forename: Tolek
authors.initials: T
authors.lastname: Tyliszczak
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.
authors.forename: David A
authors.initials: DA
authors.lastname: Shapiro
mesh_terms: D052203:Ferrosoferric Oxide / Q000378:metabolism; D008280:Magnetics; D055944:Magnetosomes / Q000378:metabolism*; D042201:Magnetospirillum / Q000166:cytology*; D008853:Microscopy / Q000295:instrumentation* / Q000379:methods*; D011859:Radiography; D012244:Rhodospirillaceae / Q000166:cytology*; D013057:Spectrum Analysis; D014965:X-Rays
chemical_list: D052203:Ferrosoferric Oxide
keywords: STXM; XAS-XMCD; biomineralization; magnetotactic bacteria; ptychography