Coral endosymbiont growth is enhanced by metabolic interactions with bacteria

• Published in: Nature communications Vol. 14; no. 1; p. 6864
• Main Authors: Matthews, Jennifer L., Khalil, Abeeha, Siboni, Nachshon, Bougoure, Jeremy, Guagliardo, Paul, Kuzhiumparambil, Unnikrishnan, DeMaere, Matthew, Le Reun, Nine M., Seymour, Justin R., Suggett, David J., Raina, Jean-Baptiste
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 27-10-2023; Nature Publishing Group; Nature Portfolio
• Subjects: 13/31; 14; 14/63; 45; 45/23; 49; 631/326/2565/547; 631/45/320; 704/829/826; Acetic acid; Algae; Aquatic microorganisms; Bacteria; Coral reefs; Corals; Endosymbionts; Humanities and Social Sciences; Indoleacetic acid; Labrenzia; Marinobacter; Metabolism; Metabolites; Microalgae; Microorganisms; Monosaccharides; multidisciplinary; Science; Science (multidisciplinary); Stable isotopes; Symbiodiniaceae; Symbionts
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-023-42663-y

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.
A new study reveals that bacterial partners supply essential metabolites to the vital microalgal symbionts of corals, including metabolites that boost symbiont growth. This breakthrough increases our understanding of coral microbial ecology and also opens the door to innovative ways of protecting coral reefs.