0045.08. Myriam Claeys, Olivier Leroux and Wim Bert are gratefully acknowledged for electron microscopy assistance. We sincerely thank Heroen Verbruggen check details and Lennert Tyberghein for collecting the specimens. Electronic supplementary material Additional file 1: Transmission electron micrograph of vegetative Bryopsis thallus in longisection. Figure A: the outer cytoplasmic layer (ol) adjacent to the Bryopsis cell wall (cw) contains most of the organelles excluding only the chloroplasts (chl), which are present in the inner layer next to the central vacuole (cv). Magnification: × 8000, Scale bar: 3 μm. Figure B (detail of Figure A): besides

mitochondria (m), endoplasmic reticulum and vacuolar evaginations (v), endogenous bacteria (ba) are present in the outer cytoplasmic layer. Magnification: × 25000, Scale bar: 1 μm. (PDF 827 KB) Additional file 2: The marker used as a normalization and identification tool in all DGGE

analyses. This marker covers the full range of endophytic (including chloroplast) sequences previously obtained from Bryopsis samples MX19, MX90, MX164, MX263 and MX344 [3]. For each marker band, the band name (M1m, M1b, M2-M10), taxonomic identification, clone reference and accession number are represented. (PDF 913 KB) References 1. Burr FA, West JA: Light and electron microscope observations on the vegetative and reproductive structures of Bryopsis hypnoides . this website Phycologia 1970,9(1):17–37.CrossRef 2. Burr FA, Evert RF: Cytochemical study of wound-healing protein in Bryopsis hypnoides . Cytobios 1972,6(24):199–215. 3. Hollants J, Leroux O, Leliaert DMXAA in vivo F, Decleyre H, De Clerck O, Willems A: Who is in there? Exploration PJ34 HCl of endophytic bacteria within the siphonous green seaweed Bryopsis (Bryopsidales, Chlorophyta). PLoS ONE 2011,6(10):e26458.PubMedCrossRef 4. Lachnit T,

Meske D, Wahl M, Harder T, Schmitz R: Epibacterial community patterns on marine macroalgae are host-specific but temporally variable. Environ Microbiol 2011,13(3):655–665.PubMedCrossRef 5. Burke C, Thomas T, Lewis M, Steinberg P, Kjelleberg S: Composition, uniqueness and variability of the epiphytic bacterial community of the green alga Ulva australis . ISME J 2011,5(4):590–600.PubMedCrossRef 6. Meusnier I, Olsen JL, Stam WT, Destombe C, Valero M: Phylogenetic analyses of Caulerpa taxifolia (Chlorophyta) and of its associated bacterial microflora provide clues to the origin of the Mediterranean introduction. Mol Ecol 2001,10(4):931–946.PubMedCrossRef 7. Goecke F, Labes A, Wiese J, Imhoff JF: Chemical interactions between marine macroalgae and bacteria. Mar Ecol-Prog Ser 2010, 409:267–299.CrossRef 8. Johnson CR, Muir DG, Reysenbach AL: Characteristic bacteria associated with surfaces of coralline algae – a hypothesis for bacterial induction of marine invertebrate larvae. Mar Ecol-Prog Ser 1991,74(2–3):281–294. 9. Mine I, Menzel D, Okuda K: Morphogenesis in giant-celled algae. In International Review of Cell and Molecular Biology. Volume 266.