Abstract
‘Candidatus Endobugula sertula,’ the uncultivated γ-proteobacterial symbiont of the marine bryozoan Bugula neritina, synthesizes bryostatins, complex polyketides that render B. neritina larvae unpalatable to predators. Although the symbiosis is well described, little is known about the locations of ‘E. sertula’ or the bryostatins throughout larval settlement, metamorphosis and early development. In this study, we simultaneously localized ‘E. sertula’ and the bryostatins in multiple stages of the B. neritina life cycle, using a novel bryostatin detection method based on its known ability to bind mammalian protein kinase C. Our results suggest that the bryostatins are deposited onto the exterior of B. neritina larvae during embryonic development, persist on the larval surface throughout metamorphosis and are shed prior to cuticle formation. During metamorphosis, ‘E. sertula’ remains adhered to the larval pallial epithelium and is incorporated into the preancestrula cystid tissue layer, which ultimately develops into a bud and gives rise to the next zooid in the colony. Colocalization of bryostatin signal with aggregates of ‘E. sertula’ in buds of ancestrulae suggested new synthesis of bryostatins in ancestrulae. In adult B. neritina colonies, symbiont microcolonies were observed in the funicular cords of rhizoids, which likely result in asexual transmission of ‘E. sertula’ to regenerated colonies. Furthermore, bryostatin signal was detected on the surface of the rhizoids of adult B. neritina colonies. Through simultaneous localization of the bryostatins and the ‘E. sertula,’ we determined how ‘E. sertula’ is transmitted, and identified shifts in bryostatin localization throughout the life cycle of the host B. neritina.
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Acknowledgements
We thank C Sheehan, R McConaughey, D Edwards, E Kisfaludy, C Anderson and S Sudek for assistance with B. neritina collection. G Lim provided B. simplex and B. turrita larvae, A Newton helped with initial design of the bryostatin detection method and H Trapido-Rosenthal advised on protocols for settlement induction. We also thank Sandra Oster, two anonymous reviewers and an editor for comments that improved this manuscript. This work was funded by California Sea Grant (R/MP-88), the National Institutes of Health (grant 5R01CA079678-03) and the Scripps Institution of Oceanography Graduate Student Office. KHS was supported by the Los Angeles ARCS Foundation. SKD was supported by NSF Grant IOB 0345049.
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Sharp, K., Davidson, S. & Haygood, M. Localization of ‘Candidatus Endobugula sertula’ and the bryostatins throughout the life cycle of the bryozoan Bugula neritina. ISME J 1, 693–702 (2007). https://doi.org/10.1038/ismej.2007.78
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DOI: https://doi.org/10.1038/ismej.2007.78
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