The coral microbiome: towards an understanding of the molecular mechanisms of coral-microbiota interactions

Corals live in intimate relationships with an intricate collection of microbes that are crucial for their functioning; therefore, understanding the molecular basis of the interactions of the coral host and its associated microbiome is vital for coral resilience in a warming ocean. Corals live in a complex, multipartite symbiosis with diverse microbes across kingdoms, some of which are implicated in vital functions, such as those related to resilience against climate change. However, knowledge gaps and technical challenges limit our understanding of the nature and functional significance of complex symbiotic relationships within corals. Here, we provide an overview of the complexity of the coral microbiome focusing on taxonomic diversity and functions of well-studied and cryptic microbes. Mining the coral literature indicate that while corals collectively harbour a third of all marine bacterial phyla, known bacterial symbionts and antagonists of corals represent a minute fraction of this diversity and that these taxa cluster into select genera, suggesting selective evolutionary mechanisms enabled these bacteria to gain a niche within the holobiont. Recent advances in coral microbiome research aimed at leveraging microbiome manipulation to increase coral's fitness to help mitigate heat stress-related mortality are discussed. Then, insights into the potential mechanisms through which microbiota can communicate with and modify host responses are examined by describing known recognition patterns, potential microbially derived coral epigenome effector proteins and coral gene regulation. Finally, the power of omics tools used to study corals are highlighted with emphasis on an integrated host-microbiota multiomics framework to understand the underlying mechanisms during symbiosis and climate change-driven dysbiosis.

Automated summary

Understanding the complex interactions between corals and their associated microbiome is essential for coral resilience in a warming ocean. Recent research focuses on manipulating the coral microbiome to enhance their ability to withstand stress. The potential mechanisms through which microbiota communicate with and modify host responses, as well as the power of omics tools in studying corals, are highlighted.