Confocal microscope images of colonized glass beads. Diatoms (Navicula sp. 1) are seen by the red fluorescence of their chloroplast. Bacteria (P. haloplanktis) are stained with SYBR Green 1. (a) and (d) Diatoms alone; (b) and (e) P. haloplanktis added to the diatom culture after 4 d; (c) and (f) P. haloplanktis added to diatom culture at time zero. Upper panel magnification was 10006 × , lower panel magnification was 23006 ×.