Figure 3.

Visualisation of algae Ulva mutabilis grown under axenic conditions or with bacterial symbionts Roseovarius sp. MS2 and Maribacter sp. MS6. a) Images acquired after nucleic acid staining with SYBR gold and with confocal laser scanning microscopy. The protrusion of alga grown without bacterial symbiont is highlighted (red arrow). DIC: differential interference microscopy. b) The images show ectoine spatial localisation and thus the presence of Roseovarius sp. (m/z 143.0814 for [M + H]⁺, m/z 165.0633 for [M + Na]⁺, shown in green) as well as chlorophyll (m/z 892.5360 for [M + H]⁺, m/z 614.2375 fragment shown in white). These metabolite traces are visible in axenic algae, symbiotic algae, and cell cultures of bacteria Roseovarius sp. MS2. White arrows indicate the rhizoidal zones.