[Effects of Microplastic Exposure on the Community Structure and Function of Symbiotic Bacteria in <i>Sinularia microclavata</i>].

Microplastics are widely distributed in the marine environment and are harmful to the health of marine organisms (including corals). However, studies on the impact of microplastics on coral have been very limited, and the specific mechanism of their impact is not clear. Therefore, in this study, microplastic PA, which is common in the marine environment, was selected to conduct a 7-day microplastic exposure experiment on <i>Sinularia microclavata</i>. The effects of microplastic exposure at different times on the diversity, community structure, and function of the symbiotic bacterial community of coral were analyzed using high-throughput sequencing technology. The <i>α</i>-diversity of the symbiotic bacterial community of coral first decreased and then increased with the exposure time of microplastics. The analysis of <i>β</i>-diversity and microbial community composition showed that microplastic exposure caused significant changes in the symbiotic bacterial community of coral, and the bacterial community composition also changed with the exposure time. A total of 49 phyla, 152 classes, 363 orders, 634 families, and 1390 genera were detected. At the phylum level, Proteobacteria was the dominant taxa in all samples, but the relative abundance varied among samples. Microplastic exposure increased the abundance of Proteobacteria, Chloroflexi, Firmicutes, Actinobacteriota, Bacteroidota, and Acidobacteriota. At the genus level, <i>Ralstonia, Acinetobacter</i>, and <i>Delftia</i> were the dominant taxa of symbiotic bacteria of coral after microplastic exposure. PICRUSt functional prediction indicated that functions of the coral symbiotic bacterial community, including signal transduction, cellular community prokaryotes, xenobiotics biodegradation and metabolism, and cell motility, decreased after microplastic exposure on coral. BugBase phenotype predictions indicated that microplastic exposure altered three phenotypes (pathogenic, anaerobic, and oxidative stress-tolerant) of the coral symbiotic bacterial community. FAPROTAX functional predictions indicated that microplastic exposure caused significant changes in functions such as the symbiotic relationship between coral symbiotic bacteria and the host, carbon and nitrogen cycling, and photosynthesis. This study provided basic data on the mechanism of microplastic impacts on corals and microplastics ecotoxicology.