Arnaud-Haond, S., Aires, T., Candeias, R., Teixeira, S. J. L., Duarte, C. M., Valero, M., et al. (2017). Entangled fates of holobiont genomes during invasion: nested bacterial and host diversities in Caulerpa taxifolia. Mol. Ecol., 26(8), 2379–2391.
Résumé: Successful prevention and mitigation of biological invasions requires retracing the initial steps of introduction, as well as understanding key elements enhancing the adaptability of invasive species. We studied the genetic diversity of the green alga Caulerpa taxifolia and its associated bacterial communities in several areas around the world. The striking congruence of alpha and beta diversity of the algal genome and endophytic communities reveals a tight association, supporting the holobiont concept as best describing the unit of spreading and invasion. Both genomic compartments support the hypotheses of a unique accidental introduction in the Mediterranean and of multiple invasion events in southern Australia. In addition to helping with tracing the origin of invasion, bacterial communities exhibit metabolic functions that can potentially enhance adaptability and competitiveness of the consortium they form with their host. We thus hypothesize that low genetic diversities of both host and symbiont communities may contribute to the recent regression in the Mediterranean, in contrast with the persistence of highly diverse assemblages in southern Australia. This study supports the importance of scaling up from the host to the holobiont for a comprehensive understanding of invasions.
|
Nguyen-Kim, H., Bouvier, T., Bouvier, C., Bui, V. N., Le-Lan, H., & Bettarel, Y. (2015). Viral and Bacterial Epibionts in Thermally-Stressed Corals. Journal of Marine Science and Engineering, 3(4), 1272–1286.
Résumé: The periodic rise in seawater temperature is one of the main environmental determinants of coral bleaching. However, the direct incidence of these episodic thermal anomalies on coral-associated microbiota and their subsequent effects on coral health are still not completely understood. In this study, we investigated the dynamics of three main microbial communities of the coral holobiont (e.g., Symbiodinium, bacteria and viruses), during an experimental thermal stress (+4 °C) conducted on the scleractinian Fungia repanda. The heat-treatment induced coral bleaching after 11 days and resulted in a final elevation of ca. 9, 130 and 250-fold in the abundance of mucosal viruses, bacteria, and Symbiodinium, respectively. On the contrary, the proportion of actively respiring bacterial cells declined by 95% in heat-stressed corals. The community composition of epibiotic bacteria in healthy corals also greatly differed from bleached ones, which also exhibited much higher production rates of viral epibionts. Overall, our results suggest that the shift in temperature induced a series of microbial changes, including the expulsion and transfer of Symbiodinium cells from the coral polyps to the mucus, the collapse of the physiological state of the native bacterial associates, a substantial alteration in their community structure, and accompanied by the development of a cortege of highly active virulent phages. Finally, this study provides new insights into the environmentally-driven microbial and viral processes responsible for the dislocation of the coral holobiont.
|
