Vibrio coralliilyticus

  • Coral pathogen

Overview

Vibrio coralliilyticus is a Gram-negative marine bacterium that poses a significant threat to corals and other invertebrates in both natural reef environments and marine aquariums. Originally discovered in 2002, this temperature-dependent pathogen has emerged as one of the most important bacterial causes of coral disease worldwide, making it a critical concern for aquarium hobbyists maintaining reef systems.

Affected species (hosts)

Corals:

  • Hard corals including Pocillopora damicornis (the original host species)
  • Montipora species (particularly M. capitata in Hawaiian systems)
  • Caribbean species like Montastraea cavernosa and Orbicella faveolata
  • Mediterranean corals including Oculina patagonica and Cladocora caespitosa

Other Invertebrates:

  • Shellfish larvae (Pacific oysters, Eastern oysters, Kumamoto oysters)
  • Soft corals and gorgonians

How Does V. coralliilyticus Cause Disease?

Temperature-Dependent Virulence. The bacterium demonstrates remarkable temperature-dependent pathogenicity, becoming significantly more aggressive at elevated temperatures above 27°C (80°F).

  • 24-25°C: Causes coral bleaching through disruption of symbiotic algae
  • 27-29°C: Triggers acute tissue loss and rapid coral mortality
  • Above 29°C: Maximum virulence with potential for complete colony loss

Toxin Production: V. coralliilyticus produces a potent zinc-metalloprotease (VcpA) that serves as its primary virulence factor. This enzyme inhibits photosynthesis in coral symbiotic algae (Symbiodinium), and causes direct tissue damage and lysis. 

Advanced Secretion Systems: The bacterium employs sophisticated Type VI secretion systems (T6SS) to inject toxins directly into coral cells and eliminate beneficial bacteria. Recent research has identified at least 9 novel anti-eukaryotic toxins delivered through these systems.

Microbiome Disruption: Infection leads to breakdown of the coral’s normal microbial community, making it easier for other pathogens to invade and for disease to progress. V. coralliilyticus can trigger prophage induction in beneficial bacteria, giving it a competitive advantage.

Opportunistic Behavior: While capable of acting as a primary pathogen, V. coralliilyticus often worsens existing diseases or exploits stressed corals. In the ongoing Stony Coral Tissue Loss Disease (SCTLD) outbreak in Florida, V. coralliilyticus-positive corals show 100% mortality compared to only 21-33% in pathogen-negative fragments.

Management and Prevention Strategies

Prevention. Quarantine new coral arrivals for 2-4 weeks minimum, with separate filtration for quarantine systems.  

Testing. Test new arrivals in the QT to make sure they’re pathogen-free before introducing them to your display. 

Lower the temperature. Reduce temperature to at least below 26C (78.8F), ideally below 24C (75.2F). 

Avoid broad-spectrum antibiotics: Most strains show high resistance to amoxicillin and kanamycin. 

If you must use antibiotics: Most Vibrio species are susceptible to Ciprofloxacin. Also consider Oxalinic Acid. While there’s no direct study testing oxalinic acid specifically against V. coralliilyticus, the fact that nalidixic acid (another quinolone) is effective at low concentrations suggests that oxalinic acid will also be effective, since both drugs operate through the same mechanism.

But first see this note about the use of antibiotics in aquariums! 

V. coralliilyticus in reef tanks

Prevalence

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Considering the prevalence of this pathogen in other tanks can help you gauge whether finding it in your tank is expected or unusual.

Abundance Distribution

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Comparing the levels of this pathogen in your tank with those found in other tanks provides a context for interpreting your test results. 

References

Ushijima, B., et al. (2020). Disease diagnostics and potential coinfections by Vibrio coralliilyticus during an ongoing coral disease outbreak in Florida. Frontiers in Microbiology, 11, 569354. https://doi.org/10.3389/fmicb.2020.569354

Lydick, V., et al. (2024). Quorum sensing regulates virulence factors in the coral pathogen Vibrio coralliilyticus. Applied and Environmental Microbiology, 90(15), e01143-24. https://doi.org/10.1128/aem.01143-24

Xu, M., et al. (2024). Mitigation of Vibrio coralliilyticus-induced coral bleaching through bacterial dysbiosis prevention by Ruegeria profundi. Applied and Environmental Microbiology, 90(4), e02274-23. https://doi.org/10.1128/aem.02274-23

Wang, W., et al. (2024). High temperatures increase the virulence of Vibrio bacteria towards their coral host and competing bacteria via type VI secretion systems. PLOS Biology, 22(9), e3002788. https://doi.org/10.1371/journal.pbio.3002788

Mass, S., et al. (2024). The coral pathogen Vibrio coralliilyticus uses a T6SS to secrete a group of novel anti-eukaryotic effectors that contribute to virulence. PLOS Biology, 22(9), e3002734. https://doi.org/10.1371/journal.pbio.3002734

Kimes, N.E., et al. (2011). Temperature regulation of virulence factors in the pathogen Vibrio coralliilyticus. The ISME Journal, 6(4), 835-846. https://doi.org/10.1038/ismej.2011.154

Ushijima, B., et al. (2014). Vibrio coralliilyticus strain OCN008 is an etiological agent of acute Montipora white syndrome. Applied and Environmental Microbiology, 80(7), 2102-2109. https://pmc.ncbi.nlm.nih.gov/articles/PMC3993142/

Rubio-Portillo, E., et al. (2020). Virulence as a side effect of interspecies interaction in Vibrio coral pathogens. mBio, 11(4), e00201-20. https://doi.org/10.1128/mbio.00201-20

Zhou, Z., et al. (2019). Altered immune landscape and disrupted coral-Symbiodinium symbiosis in the scleractinian coral Pocillopora damicornis by Vibrio coralliilyticus challenge. Frontiers in Physiology, 10, 366. https://doi.org/10.3389/fphys.2019.00366

Ushijima, B., et al. (2018). Factors affecting infection of corals and larval oysters by Vibrio coralliilyticus. PLoS ONE, 13(6), e0199475. https://doi.org/10.1371/journal.pone.0199475

Ushijima, B., et al. (2022). Comparison of Vibrio coralliilyticus virulence in Pacific oyster larvae and corals. Microbiology, 168(4). https://doi.org/10.1099/mic.0.001169

Wang, S., et al. (2024). Microbial community and transcriptional responses to V. coralliilyticus stress in coral Favites halicora and Pocillopora damicornis holobiont. Marine Environmental Research, 196, 106394. https://doi.org/10.1016/j.marenvres.2024.106394

Khodzori, F., et al. (2021). Pathogenic Vibrio spp. identified for white syndrome coral disease in Tioman Island Marine Park, Malaysia. Malaysian Journal of Microbiology. https://doi.org/10.21161/mjm.200859