title: Correlative electron and fluorescence microscopy of magnetotactic bacteria in liquid: toward in vivo imaging.
abstract: Magnetotactic bacteria biomineralize ordered chains of uniform, membrane-bound magnetite or greigite nanocrystals that exhibit nearly perfect crystal structures and species-specific morphologies. Transmission electron microscopy (TEM) is a critical technique for providing information regarding the organization of cellular and magnetite structures in these microorganisms. However, conventional TEM can only be used to image air-dried or vitrified bacteria removed from their natural environment. Here we present a correlative scanning TEM (STEM) and fluorescence microscopy technique for imaging viable cells of Magnetospirillum magneticum strain AMB-1 in liquid using an in situ fluid cell TEM holder. Fluorescently labeled cells were immobilized on microchip window surfaces and visualized in a fluid cell with STEM, followed by correlative fluorescence imaging to verify their membrane integrity. Notably, the post-STEM fluorescence imaging indicated that the bacterial cell wall membrane did not sustain radiation damage during STEM imaging at low electron dose conditions. We investigated the effects of radiation damage and sample preparation on the bacteria viability and found that approximately 50% of the bacterial membranes remained intact after an hour in the fluid cell, decreasing to ~30% after two hours. These results represent a first step toward in vivo studies of magnetite biomineralization in magnetotactic bacteria.
authors.affiliation: Emergent Atomic and Magnetic Structures, Division of Materials Sciences and Engineering, Ames Laboratory, Ames, IA 50011, USA.
authors.forename: Taylor J
authors.initials: TJ
authors.lastname: Woehl
authors.affiliation: Emergent Atomic and Magnetic Structures, Division of Materials Sciences and Engineering, Ames Laboratory, Ames, IA 50011, USA.
authors.forename: Sanjay
authors.initials: S
authors.lastname: Kashyap
authors.affiliation: Emergent Atomic and Magnetic Structures, Division of Materials Sciences and Engineering, Ames Laboratory, Ames, IA 50011, USA.
authors.forename: Emre
authors.initials: E
authors.lastname: Firlar
authors.affiliation: Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14424 Potsdam, Germany.
authors.forename: Teresa
authors.initials: T
authors.lastname: Perez-Gonzalez
authors.affiliation: Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14424 Potsdam, Germany.
authors.forename: Damien
authors.initials: D
authors.lastname: Faivre
authors.affiliation: School of Life Sciences, University of Nevada at Las Vegas, Las Vegas, NV 89154, USA.
authors.forename: Denis
authors.initials: D
authors.lastname: Trubitsyn
authors.affiliation: School of Life Sciences, University of Nevada at Las Vegas, Las Vegas, NV 89154, USA.
authors.forename: Dennis A
authors.initials: DA
authors.lastname: Bazylinski
authors.affiliation: Emergent Atomic and Magnetic Structures, Division of Materials Sciences and Engineering, Ames Laboratory, Ames, IA 50011, USA.
authors.forename: Tanya
authors.initials: T
authors.lastname: Prozorov
mesh_terms: D042201:Magnetospirillum / Q000166:cytology* / Q000648:ultrastructure*; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence