Validation of bacterial cell labeling with iron oxide particles. Fluorescence microscopy of S. aureus bacteria (strain 6850) labeled with Syto 9 (green) and rhodamine-labeled 5-nm citrate-coated iron oxide nano particles (IONPs) (red) using different labeling strategies: (A) electroporation of electro-competent bacterial cells, (B) incubation of unmodified bacterial cells and (C) incubation of electro-competent bacterial cells. Syto 9 was used for co-registration. (D) S. aureus bacteria labeled with 5-nm amine-coated IONPs by incubation of electro-competent bacterial cells. Electron microscopy images of S. aureus bacterial cell samples labeled by (E) electroporation and (F) incubation show a high percentage of cell debris when the electroporation technique was used (yellow arrowheads in (E)) and clusters of IONPs bound to the surface of intact bacteria (yellow arrows in (F)).
Hoerr et al. BMC Biology 2013 11:63 doi:10.1186/1741-7007-11-63