FIG. 2.

Transmission electron micrograph of a thin section of an untreated strain PAO1 cell. The cell (whose surface is indicated by arrows) is difficult to distinguish from the embedding resin due to the lack of electron-dense elements in the sample. Bar = 200 nm. (Inset) EDS spectrum obtained from an untreated PAO1 cell, showing peaks for oxygen, phosphorus, chlorine, iron, and copper. The first four peaks correspond to elements present in the sample. The large copper peaks were generated by the supporting grid. Similar results were obtained for all four strains.