The microbiome of the branching coral Acropora kenti

Abstract

Abstract Microbial diversity has been extensively explored in reef-building corals however the functional roles of coral-associated microorganisms remain poorly elucidated. Here, metagenome-assembled genomes (MAGs) were recovered from the coral Acropora kenti (formerly A. tenuis) to elucidate microbial functions and metabolic interactions within the holobiont. Overall, 191 bacterial and 10 archaeal MAGs assigned to 16 phyla were recovered from A. kenti and the adjacent seawater. Based on their prevalence and relative abundances, 82 of these MAGs were specific to the A. kenti holobiont, including members of the Proteobacteria, Bacteroidota, and Desulfobacterota. A. kenti-specific MAGs displayed significant differences in their genomic features and functional potential relative to seawater specific-MAGs, having a higher prevalence of genes involved in host immune system evasion, nitrogen and carbon fixation, and synthesis of five essential B-vitamins. Moreover, a diversity of A. kenti-specific MAGs encoded genes required for the synthesis 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 correlated to increased temperature and dissolved inorganic nitrogen. Corresponding enrichment in molecular chaperones, nitrate reductases, and a heat-shock protein, indicated phenotypic adaptation of the microbiome to localised anthropogenic pressures. These findings reveal mechanisms of A. kenti-microbiome-symbiosis on the Great Barrier Reef, highlighting the interactions underpinning the health and functioning of this keystone holobiont.