Multi-domain probiotic consortium as an alternative to chemical remediation of oil spills at coral reefs and adjacent sites

Abstract

Background Beginning in the last century, coral reefs have suffered the consequences of anthropogenic activities, including oil contamination. Chemical remediation methods, such as dispersants, can cause substantial harm to corals and reduce their resilience to stressors. To evaluate the impacts of oil contamination and find potential alternative solutions to chemical dispersants, we conducted a mesocosm experiment with the fire coral Millepora alcicornis, which is sensitive to environmental changes. We exposed M. alcicornis to a realistic oil-spill scenario in which we applied an innovative multi-domain bioremediator consortium (bacteria, filamentous fungi, and yeast) and a chemical dispersant (Corexit® 9500, one of the most widely used dispersants), to assess the effects on host health and host-associated microbial communities. Results The selected multi-domain microbial consortium helped to mitigate the impacts of the oil, substantially degrading the polycyclic aromatic and n-alkane fractions and maintaining the physiological integrity of the corals. Exposure to Corexit 9500 negatively impacted the host physiology and altered the coral-associated microbial community. After exposure, the abundances of certain bacterial genera such as Rugeria and Roseovarius increased, as previously reported in stressed or diseased corals. We also identified several bioindicators of Corexit 9500 in the microbiome. The impact of Corexit 9500 on the coral health and microbial community was far greater than oil alone, killing corals after only 4 days of exposure in the flow-through system. In the treatments with Corexit 9500, the action of the bioremediator consortium could not be observed directly because of the extreme toxicity of the dispersant to M. alcicornis and its associated microbiome. Conclusions Our results emphasize the importance of investigating the host-associated microbiome in order to detect and mitigate the effects of oil contamination on corals and the potential role of microbial mitigation and bioindicators as conservation tools. Chemical dispersants were far more damaging to corals and their associated microbiome than oil, and should not be used close to coral reefs. This study can aid in decision-making to minimize the negative effects of oil and dispersants on coral reefs.

Coral microbiome manipulation elicits metabolic and genetic restructuring to mitigate heat stress and evade mortality

“…Despite the diversity of the coral microbiome, which makes it challenging to decipher the contribution of associated microbes to coral holobiont biology, the dynamic nature of the coral microbiome, which can often change markedly-e.g., across sites, species, age, and under stress-further hampers the ability to conduct such studies in the natural environment (15,(19)(20)(21). For this reason, manipulation of BMCs in controlled experimental setups, such as mesocosms (22)(23)(24), provides an avenue to identify important microbial players and study holobiont responses (and putative underlying mechanisms), while maintaining a quasi-reef environment, to improve and inform the development of biotechnological solutions to promote coral reef resilience.…”

Harnessing the microbiome to prevent global biodiversity loss

“…In the face of such alarming challenges, recent advances in research have indicated the potential of microbiome-based interventions, such as probiotics to protect wildlife and mitigate environmental impacts, and microbiome transplants to restore ecosystems and improve their resilience [10][11][12][13][14][15][16][17][18][19][20][21] . We explore synergies between different disciplines, synthesize basic microbiome engineering and symbiosis concepts, and identify critical challenges and safety issues.…”

Host under epigenetic control: A novel perspective on the interaction between microorganisms and corals

“…[ 66 ] showed that coral bleaching could be reduced in the presence of the pathogen Vibrio coralliilyticus at normal and high temperatures. Although BMCs have been shown to aid in coral resistance [ 66,77–79 ] , [Santoro et al, 2021 ‐ https://advances.sciencemag.org/content/7/33/eabg3088] through the regulation of genes involved in the coral immune response and protection against heat stress (Santoro et al, 2021 ‐ https://advances.sciencemag.org/content/7/33/eabg3088), or even increase energy reserves and calcification rates, [ 80 ] the exact mechanisms producing the improved phenotype are not fully known. BMCs are chosen for their roles in coral holobiont nutrition and growth (via dimethylsulfoniopropionate degradation or increased cycling and provision of nutrients), removal of toxic compounds or stress mitigation (including decreasing intracellular ROS), early life development, and/or pathogen control.…”

“…[8,76] By manipulating the microbiome of P. damicornis through the addition of beneficial microorganisms for corals (BMCs), Rosado et al [66] showed that coral bleaching could be reduced in the presence of the pathogen Vibrio coralliilyticus at normal and high temperatures. Although BMCs have been shown to aid in coral resistance [66,[77][78][79] increase energy reserves and calcification rates, [80] the exact mechanisms producing the improved phenotype are not fully known. BMCs are chosen for their roles in coral holobiont nutrition and growth (via dimethylsulfoniopropionate degradation or increased cycling and provision of nutrients), removal of toxic compounds or stress mitigation (including decreasing intracellular ROS), early life development, and/or pathogen control.…”