Corals survive heat thanks to probiotic bacteria

KAUST researchers are exploring the use of probiotic bacteria to increase coral survival after bleaching events. Credit: © 2021 KAUST; Morgan bennett smith

Treating corals with a probiotic cocktail of beneficial bacteria increases survival after a bleaching event, new research shows. This approach could be applied before an expected heat wave to help corals recover from high sea temperatures.

Climate change increases ocean temperatures, disrupting the relationship between corals and their symbiotic photosynthetic algae and causing corals to bleach, in some cases leading to their death. KAUST researchers proposed that manipulating the coral microbiome could improve their stress tolerance using microorganisms beneficial to corals, or BMCs.

To test this, the team selected six beneficial bacterial strains isolated from coral. Mussismilia hispida and used them to inoculate experimental cultures of M. hispida. At the same time, the corals were subjected to heat stress treatment, the temperature rising to 30 degrees. Celsius for 10 days before dropping back to 26 degrees Celsius. Researchers monitored coral health and measured microbial diversity and metabolic parameters in treatments with and without probiotics or heat stress.

Widespread bleaching of coral

Climate change and warming seas are having a devastating impact on coral reefs, causing widespread coral bleaching like the one pictured above. Credit: © 2021 KAUST; Morgan Bennett Smith.

Initially, there was no difference – corals with and without probiotics reacted the same at maximum temperature and both bleached. “At this point in the experiment, I thought, well, okay, we’re seeing similar responses between treatments,” recalls Erika Santoro, the study’s lead author, who is now a postdoctoral fellow at KAUST. “But then, after turning down the temperature, we observed a rebound in the group that we treated with BMC probiotic. It was a very nice surprise. “

The probiotic treatment improved the response and recovery of corals after the heat stress event, increasing survival from 60% to 100%. Researchers interpret this as a BMC helping the holobiont mitigate the effects of “post-heat stress disorder” and thus restructure physiological and metabolic profiles.

The research also describes some of the protective molecular mechanisms. During the recovery period, BMC-treated corals showed lower expression of genes involved in apoptosis and cell reconstruction, and increased expression of heat stress protection genes. The BMC treatment also altered the profile of the microbiome by incorporating some of the beneficial bacteria as well as other changes in the structure of the population.

BMCs are a valuable tool in dealing with the consequences of climate change, but Santoro stresses that this is not a quick fix. “Using a probiotic is an effective tool in helping corals cope with heat stress, but we also need to consider other interventions,” she says, such as “protection and conservation, everyone being more aware and, above all, decreasing greenhouse gas emissions and trying to change our use of resources Corals will need all of these interventions.

Reference: “The manipulation of the microbiome of corals induces metabolic and genetic restructuring to alleviate heat stress and escape mortality” by Erika P. Santoro, Ricardo M. Borges, Josh L. Espinoza, Marcelo Freire, Camila SMA Messias, Helena DM Villela, Leandro M. Pereira, Caren LS Vilela, João G. Rosado, Pedro M. Cardoso, Phillipe M. Rosado, Juliana M. Assis, Gustavo AS Duarte, Gabriela Perna, Alexandre S. Rosado, Andrew Macrae, Christopher L. Dupont, Karen E. Nelson, Michael J. Sweet, Christian R. Voolstra and Raquel S. Peixoto, August 13, 2021, Scientists progress.
DOI: 10.1126 / sciadv.abg3088

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