Coral Mucus Microbial Community Change and Resistant Strategy Under UV Radiation: A Case from Porites sp. and Favites...

Coral mucus serves as a crucial defensive barrier for corals, where the mucus microbes play a vital role in the coral's resistance to external stresses. However, detailed knowledge of the effect of UV radiation on coral mucus microbiome is limited, particularly regarding the UV resistance mechanisms of coral mucus microbes. This study investigates changes in the mucus microbial community and possible UV-resistant mechanisms of the mucus microbiota of Porites sp. and Favites sp. under UV stress using high-throughput sequencing, UV-resistant microbial isolation, and RT-qPCR analysis. Compared to the control, UV stress alters microbial community structure by reducing microbial diversity, e.g., the relative abundance of Aquibacter, Agaribacter, and Oleibacter in coral Porites sp., and the Roseobacter clade CHAB_I_5 lineage, Roseivirga, and Nautella in coral Favites sp. increase under UV stress. Meanwhile, it is indicated that the Favites sp. mucus microbiome is much more sensitive than the Porites sp. mucus microbiome. A total of 428 microbial strains belonging to 5 phyla, 7 classes, 15 orders, 23 families, and 47 genera were isolated from these two coral mucus species, with Ruegeria and Rossellomorea as the most abundant cultured taxa. Pseudoalteromonas galatheae strain P12 and Limimaricola pyoseonensis strains P2 and P9 have been proven to exhibit higher UV resistance by enhanced expression of tyr, sod, gogat, and uvrC genes, indicating that the UV resistance of coral mucus bacteria involves complex molecular processes, including upregulation of antioxidant enzyme expression and enhancement of melanin and glutamic acid biosynthesis. These findings enhance our understanding of coral mucus microbial ecological functions, particularly highlighting the coral mucus microbial UV resistance strategy.