Microbial Pathogenesis in Coral Reef Ecosystems

Coral reefs depend on a delicate association between the animal host and its diverse microbial community, collectively the holobiont. Under stable conditions, symbiotic bacteria and other microbes contribute to nutrient cycling and defence against opportunistic pathogens. However, environmental stressors such as rising sea temperature, physical disturbance and overharvesting of sediment-cleaning detritivores can disrupt microbial community structure, leading to dysbiosis and proliferation of disease-causing agents. Key pathogens include species of Vibrio bacteria equipped with proteolytic enzymes and toxin-encoding genetic islands, as well as diverse assemblages of opportunistic bacteria and ciliates. Viral elements carried by bacteriophages may transfer virulence factors between strains, further complicating disease dynamics. Bleaching events and anthropogenic impacts can erode natural disease resistance in some coral genotypes, while others retain traits that suppress pathogen colonisation. Understanding these interconnections is essential for predicting disease outbreaks, guiding restoration efforts and enhancing reef resilience under changing climatic regimes.

Research from Nature Portfolio

Experimental removal of sea cucumbers from reef plots revealed that loss of these sediment-feeding detritivores sharply increases microbial pathogen loads in benthic sediments, driving dramatic rises in tissue mortality among key coral species. Investigations comparing disease-resistant and susceptible Acropora genotypes under controlled grafting assays have identified specific bacterial taxa associated with resistance phenotypes, including members of Myxococcales, while implicating the genus Sphingomonadaceae in lesion development. Genomic analyses of Vibrio coralliilyticus strains demonstrate that bacteriophage-borne toxin genes and chromosomal pathogenicity islands underpin virulence, indicating that horizontal gene transfer is a major driver of emerging coral pathogens.

Microbial Pathogenesis in Coral Reef Ecosystems publication trend

The graph below shows the total number of articles in microbial pathogenesis in coral reef ecosystems across all publications each year (not limited to Nature Index journals).

Technical terms

Holobiont: The coral animal together with its associated microbial community.

Dysbiosis: An imbalance in the normal microbial community that may permit pathogen overgrowth.

Microbiome: The collective genomes and taxa of microorganisms living in or on the coral host.

Pathogen: A microorganism capable of causing disease in its host.

Bacteriophage: A virus that infects bacteria and can transfer virulence genes between strains.

References

1. Removal of detritivore sea cucumbers from reefs increases coral disease. Nature Communications (2024).
2. Microbiome differences in disease-resistant vs. susceptible Acropora corals subjected to disease challenge assays. Scientific Reports (2019).
3. From cholera to corals: Viruses as drivers of virulence in a major coral bacterial pathogen. Scientific Reports (2015).
4. Antibiotic type and dose variably affect microbiomes of a disease-resistant Acropora cervicornis genotype. Environmental Microbiome (2025).
5. Bleaching causes loss of disease resistance within the threatened coral species Acropora cervicornis. eLife (2018).
6. Increased seawater temperature increases the abundance and alters the structure of natural Vibrio populations associated with the coral Pocillopora damicornis. Frontiers in Microbiology (2015).