# A genome-centric view of the role of the Acropora kenti microbiome in coral health and resilience

## TL;DR

This study explores the role of the Acropora kenti coral's microbiome in supporting its health and resilience to environmental stressors.

## Contribution

The study identifies specific microbial functions and metabolic interactions in the A. kenti holobiont that support host resilience.

## Key findings

- A. kenti-specific MAGs have genes for immune evasion, nitrogen fixation, and B-vitamin synthesis.
- Microbial community composition correlates with temperature and nitrogen levels, with enrichment in stress-related proteins.
- A. kenti-specific MAGs encode essential amino acid biosynthesis not possible by the host or Symbiodiniaceae.

## Abstract

Microbial diversity has been extensively explored in reef-building corals. However, the functional roles of coral-associated microorganisms remain poorly elucidated. Here, we recover 191 bacterial and 10 archaeal metagenome-assembled genomes (MAGs) from the coral Acropora kenti (formerly A. tenuis) and adjacent seawater, to identify microbial functions and metabolic interactions within the holobiont. We show that 82 MAGs were specific to the A. kenti holobiont, including members of the Pseudomonadota, Bacteroidota, and Desulfobacterota. A. kenti-specific MAGs displayed significant differences in their genomic features and functional potential relative to seawater-specific MAGs, with a higher prevalence of genes involved in host immune system evasion, nitrogen and carbon fixation, and synthesis of five essential B-vitamins. We find a diversity of A. kenti-specific MAGs encode the biosynthesis of essential amino acids, such as tryptophan, histidine, and lysine, which cannot be de novo synthesised by the host or Symbiodiniaceae. Across a water quality gradient spanning 2° of latitude, A. kenti microbial community composition is correlated to increased temperature and dissolved inorganic nitrogen, with corresponding enrichment in molecular chaperones, nitrate reductases, and a heat-shock protein. We reveal mechanisms of A. kenti-microbiome-symbiosis on the Great Barrier Reef, highlighting the interactions underpinning the health of this keystone holobiont.

This study provides insights into the functional roles of microbial symbionts within the reef-building coral Acropora kenti. The findings reveal molecular mechanisms underpinning coral health and adaptation to local environmental stressors, which may support host resilience in the face of anthropogenic climate change and pollution.