Abstract: As a result of climate change and human intervention, jellyfish outbreaks have become a serious ecological disaster that threatens coastal economies and marine ecosystems. Globally, there is an urgent need to prevent jellyfish blooms. Microorganisms play an important role in the growth and development of marine invertebrates. Co-culture experiments revealed that Bacillus paranthracis SG49 inhibited the settlement and metamorphosis of Aurelia coerulea planula larvae. The key metabolic pathways and mechanisms behind this inhibition, however, require further investigation. Using non-targeted metabolomics technology, the intracellular and extracellular metabolites of SG49 were detected, differences between the two groups were analyzed, and potential metabolites affecting planula larval metamorphosis were identified. Our results showed that SG49 intracellular and extracellular metabolites were significantly different. Specifically, seven substances were screened for their potential inhibitory activities, including 3-hydroxy-2-oxindole, kanamycin, apramycin, streptomycin, streptomycin sulfate, gallic acid, and coniferyl alcohol. Bacterial biofilms and microorganism growth can be inhibited by these metabolites. Our findings provided a theoretical basis and strain resources to prevent jellyfish outbreaks in the future.

Key words: microorganism, Aurelia coerulea, planula larvae, attachment and metamorphosis, metabolomics