CHANGES IN MICROBIAL COMMUNITY COMPOSITION AFFECT BIOACTIVITIES OF MUCUS ISOLATED FROM CORAL ACROPORA MILLEPORA

The metagenomics approach is quickly developing in researchs about the composition of a microbial community. In the past few decades, antibiotic resistance is increasingly popular together with emerging diseases while repeated isolation of known secondary metabolites and a decline of novel compounds in the terrestrial environment present an urgent requirement more and more in the discovery of novel marine bioactive compounds. Paired-end reads of 16S rRNA sequence of bacteria living in the coral Acropora millepora obtained by the Illumina next-generation sequencing technology to be processed by DADA2 pipeline, phyloseq, and ggplot2 packages showed that microbial composition has transformation, specifically, bleached coral mucus has an alpha diversity to be higher than healthy coral mucus. Moreover, healthy and bleached coral mucus is also used to evaluate antibacterial activity on the pandemic strain of Vibrio parahaemolyticus and identify the ability of cell cytotoxicity to HCT116 colon cancer cells. The coral surface mucus layer (SML) of healthy coral exhibited the ability of inhibition to the growth of the disease strain is higher than that of bleached coral at all concentrations (10 – 30 µL). The cytotoxicity of colon cancer cell line HCT116 was also clearly observed when treated with healthy SML. Comparison of cytotoxicity of two mucus types shows that healthy coral mucus has inhibition to colon cancer cell line to be 1.5 times higher than mucus is taken from bleached coral. The composition of the microbial community changes when corals transfer from a healthy state to a bleached one. Consequently, antibacterial activity and cytotoxicity also come down.