Distinct Host-Specific Bacterial Assemblages in Four Congeneric Pocillopora Corals Reveal a Minimal Core Microbiome...

Coral reefs, essential yet increasingly threatened marine ecosystems, rely on coral-microbiome symbioses for resilience against environmental stressors. This study investigates host-specific influences on bacterial communities in four Pocillopora species (Pocillopora eydouxi, Pocillopora meandrina, Pocillopora verrucosa, and Pocillopora woodjonesi) from the South China Sea. Using Illumina-based 16S rRNA gene sequencing, we analyzed microbiome structures, identified core taxa, and predicted metabolic functions. Results revealed that bacterial composition differed significantly among coral hosts, despite their shared habitat. P. eydouxi exhibited the highest bacterial richness and Shannon index, contrasting with minimal values in P. woodjonesi. A conserved core microbiome of 32 ASVs (1.1% of total ASVs), dominated by Gammaproteobacteria, was shared across all coral species. Host-specific enrichment of probiotic bacteria (Psychrobacter in P. eydouxi and Exiguobacterium in P. meandrina) and pathogenic taxa (e.g., Acinetobacter) was also observed. Functional prediction indicated conserved metabolic pathways across species, particularly amino acid and carbohydrate metabolism. These findings highlight host phylogeny as one of the primary determinants of microbiome assembly, providing critical insights into coral conservation strategies.