Figure 1
Symbionts colonize many different epithelial tissues in juvenile B. puteoserpentis and B. azoricus. The mussels are shown in the same orientation in all images with the anterior end on the left and the posterior end on the right. (a), (b) and (g) are B. azoricus; (c–f) are B. puteoserpentis. (a, b) Lateral view of small juvenile with (a) and without (b) shell valves. (c) Epifluorescence micrograph of a cross section (ventral view) through entire juvenile mussel. The asterisk marks the foot tip that was curled dorsally. Mussel tissue that is colonized throughout the mussel life cycle is colored in light red, whereas mussel tissues that are only infected in juveniles <9 mm are marked with a red dashed line. (d–g) Symbiont-specific FISH signals of the sulfur-oxidizing symbionts (green) and the methane-oxidizing symbionts (red) in epithelial cells of (d) gills and mantle, (e) mantle, (f) retractor muscle and (g) foot. In (e) and (f) signal overlap in a triple hybridization with the two symbiont-specific probes (red and green) and the eubacterial probe (EUB338 in yellow) makes the methane-oxidizing symbionts appear orange and the sulfur-oxidizing symbionts yellow-green. Owing to differences in signal intensity of the specific probes versus the eubacterial probe, some symbionts appear more yellow than others. The triple hybridization indicates that only the symbionts and no other bacteria are present. Nuclei of the host cells are stained with DAPI (blue).
