Vibrio shilonii

  • Coral pathogen

Overview

Vibrio shilonii is a Gram-negative marine bacterium primarily recognized as an opportunistic coral pathogen responsible for seasonal bleaching events in Mediterranean corals, particularly Oculina patagonica. This temperature-sensitive pathogen becomes virulent under elevated temperatures and environmental stress conditions. While historically associated with coral diseases, V. shilonii has also been detected in various marine invertebrates and aquaculture systems, making it a pathogen of broader marine ecological significance.

Affected species (hosts)

Primary Coral Hosts:

  • Oculina patagonica – experiences seasonal bleaching
  • Various reef-building corals in Mediterranean and other regions
  • Cold-water corals (Lophelia pertusa) – detected at low abundance
  • Pocillopora damicornis larvae – reduced survival rates

Other Marine Hosts:

  • Jellyfish – symbiotic zooxanthellae affected by V. shilonii toxins
  • Zoanthids and anemones – differential bleaching responses
  • Mollusks and fish – detected in association studies
  • Marine plankton communities

Aquaculture Hosts:

  • Farmed shrimp in Indonesia – identified as disease-causing agent
  • Various aquatic animals in culture systems

Temperature-Dependent Pathogenicity and Virulence Mechanisms

Seasonal Pathogenicity Pattern. V. shilonii exhibits classic opportunistic behavior, becoming virulent primarily under elevated temperature conditions. The bacterium causes seasonal bleaching in Mediterranean corals, with outbreaks typically occurring during warm summer months when water temperatures rise above critical thresholds.

Virulence Factor Production: The pathogen produces outer membrane vesicles (OMVs) containing signaling molecules and hydrolytic enzymes that contribute to coral tissue degradation and bleaching. These vesicles serve as delivery systems for toxins that specifically target coral symbiotic algae (zooxanthellae).

Host-Specific Toxin Effects: V. shilonii toxins cause differential bleaching responses in zooxanthellae from different coral and invertebrate hosts, indicating variable host susceptibility. Some coral species and their symbionts show greater resistance to the bacterial toxins than others.

Quorum Sensing and Environmental Response: The bacterium increases production of quorum-sensing signals in response to DMSP (dimethylsulfoniopropionate), a compound released by stressed corals. This response potentially influences coral microbiome structure and facilitates bacterial colonization during stress events.

Genetic Adaptation: Studies show that V. shilonii can exhibit increased mutation rates under pH changes, suggesting evolutionary adaptation capabilities that may enhance its pathogenic potential under changing ocean conditions.

Management and Prevention Strategies

Prevention. Quarantine new fish and corals 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. 

Temperature Control. Keep aquarium temperatures stable and avoid sudden increases that could trigger bacterial virulence. During summer months or equipment malfunctions, be especially vigilant for signs of coral bleaching or bivalve mortality.

Beware of antibiotic resistance: Antibiotic resistance is widespread in this group. Avoid antibiotic treatments if at all possible.   

If you must use antibiotics: Most Vibrio species are susceptible to Ciprofloxacin and Oxalinic Acid. 

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

V. shilonii in reef tanks

Prevalence

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Looking at how common this pathogen is 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

Li, J., Azam, F., & Zhang, S. (2016). Outer membrane vesicles containing signalling molecules and active hydrolytic enzymes released by a coral pathogen Vibrio shilonii AK1. Environmental Microbiology, 18(11), 3850-3866. https://doi.org/10.1111/1462-2920.13344

Munn, C. (2015). The Role of Vibrios in Diseases of Corals. Microbiology Spectrum, 3. https://doi.org/10.1128/microbiolspec.ve-0006-2014

Gil-Agudelo, D., Ban-Haim, Y., Rosenberg, E., & Smith, G. (2017). Differential Response of Coral Symbiotic Dinoflagellates to Bacterial Toxins that Produce Bleaching in Stony Corals. Journal of the South Carolina Academy of Science, 15, 6.

Huang, B., Peng, S., Liu, S., Zhang, Y., Wei, Y., Xu, X., Gao, C., Liu, Y., & Luo, X. (2022). Isolation, Screening, and Active Metabolites Identification of Anti-Vibrio Fungal Strains Derived From the Beibu Gulf Coral. Frontiers in Microbiology, 13. https://doi.org/10.3389/fmicb.2022.930981

Strauss, C., Long, H., Patterson, C., Te, R., & Lynch, M. (2017). Genome-Wide Mutation Rate Response to pH Change in the Coral Reef Pathogen Vibrio shilonii AK1. mBio, 8. https://doi.org/10.1128/mbio.01021-17

Sampaio, A., Silva, V., Poeta, P., & Aonofriesei, F. (2022). Vibrio spp.: Life Strategies, Ecology, and Risks in a Changing Environment. Diversity. https://doi.org/10.3390/d14020097

Ben-Haim, Y., Thompson, F., Thompson, C., Cnockaert, M., Hoste, B., Swings, J., & Rosenberg, E. (2003). Vibrio coralliilyticus sp. nov., a temperature-dependent pathogen of the coral Pocillopora damicornis. International Journal of Systematic and Evolutionary Microbiology, 53(1), 309-315. https://doi.org/10.1099/ijs.0.02402-0

Beatty, D., Clements, C., Stewart, F., & Hay, M. (2018). Intergenerational effects of macroalgae on a reef coral: major declines in larval survival but subtle changes in microbiomes. Marine Ecology Progress Series, 589, 97-114. https://doi.org/10.3354/meps12465

Zhou, Y., Guillemette, R., Malfatti, F., Zheng, T., Mao, X., Zhu, X., Medina, M., & Azam, F. (2021). Ectohydrolytic enzyme activities of bacteria associated with Orbicella annularis coral. Coral Reefs, 40, 1899-1913. https://doi.org/10.1007/s00338-021-02188-6

Tarazona, E., Lucena, T., Arahal, D., Macián, M., Ruvira, M., & Pujalte, M. (2014). Multilocus sequence analysis of putative Vibrio mediterranei strains and description of Vibrio thalassae sp. nov. Systematic and Applied Microbiology, 37(5), 320-328. https://doi.org/10.1016/j.syapm.2014.05.005