FIG. 3.

EELS spectrum of electron-dense bodies present in unstained Pseudomonas sp. strain B4. (A) Electron micrograph of an unstained cell grown in a defined medium supplemented with biphenyl as the sole carbon source. The electron-dense granule analyzed is indicated by a blue circle, and the cytoplasmic reference area analyzed is indicated by a red circle. (B) EELS spectra (after background subtraction) of the electron-dense body (PsB4_db) (blue line) and the cytoplasmic area (PsB4_CP) (red line). The spectrum of hydroxyapatite was used as the phosphate reference standard (DHP) (green line). (C) Phosphate distribution image (green), obtained by ESI superimposed with the electron micrograph negative image of Pseudomonas sp. strain B4 cells.