Coral endosymbiont growth is enhanced by metabolic interactions with bacteria

Jennifer L. Matthews, Abeeha Khalil, Nachshon Siboni, Jeremy Bougoure, Paul Guagliardo, Unnikrishnan Kuzhiumparambil, Matthew DeMaere, Nine M. Le Reun, Justin R. Seymour, David J. Suggett, Jean Baptiste Raina

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Bacteria are key contributors to microalgae resource acquisition, competitive performance, and functional diversity, but their potential metabolic interactions with coral microalgal endosymbionts (Symbiodiniaceae) have been largely overlooked. Here, we show that altering the bacterial composition of two widespread Symbiodiniaceae species, during their free-living stage, results in a significant shift in their cellular metabolism. Indeed, the abundance of monosaccharides and the key phytohormone indole-3-acetic acid (IAA) were correlated with the presence of specific bacteria, including members of the Labrenzia (Roseibium) and Marinobacter genera. Single-cell stable isotope tracking revealed that these two bacterial genera are involved in reciprocal exchanges of carbon and nitrogen with Symbiodiniaceae. We identified the provision of IAA by Labrenzia and Marinobacter, and this metabolite caused a significant growth enhancement of Symbiodiniaceae. By unravelling these interkingdom interactions, our work demonstrates how specific bacterial associates fundamentally govern Symbiodiniaceae fitness.

Original languageEnglish
Article number6864
Number of pages13
JournalNature Communications
Issue number1
Publication statusPublished - Dec 2023

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