The Microbiome After Bail-out: Testing Individual Polyps from Pocillopora verrucosa as Models for Coral Microbiology Studies

Abstract Micro-scale in vitro models are essential for the study of model organisms in highly reproducible and controlled environments. Coral research grapples with a substantial knowledge gap on micro-scale processes underlying symbiotic interactions and holobiont health, which could be addressed through the use of models adapted to microscopic studies. Individual coral polyps separated from their colonies through an acute stress-induced bail-out process have been suggested in the past as miniaturized models to study the coral holobiont. However, changes in the microbiome associated with these polyps after bail-out are still not completely understood. An aquarium experiment was therefore performed to monitor the diversity and composition of microbes of bailed-out polyps of Pocillopora verrucosa alongside their parental fragments over time. Our findings revealed no significant microbiome differences immediately following bail-out, with 80% of microbial members persisting for up to two weeks, decreasing slightly to 60% in the third week. Notably, despite a reduction in shared Amplicon Sequence Variants (ASVs), the dominant bacterial taxa's relative abundance stayed consistent across both the source fragments and bailed-out polyps for up to three weeks. This consistency underscores the potential of using micropropagates as valuable tools for microbiological research in corals. Further enhancements in polyp settlement techniques may refine these models, bolstering our capacity for comprehensive coral microbiome studies.