Bacterial diversity associated with Millepora alcicornis and Phyllogorgia dilatata corals and prospection for genes encoding bioactive molecules

Abstract

Coral reefs are marine environments with notable biodiversity, considered rich in organisms that produce active molecules. The microorganisms present in coral tissue play different roles that are not yet fully understood. The study of the microbiota can explain how microorganisms influence the health of corals and their participation in defense mechanisms. In this study, the cultivable bacterial communities of Millepora alcicornis and Phyllogorgia dilatata corals were analyzed following the steps of isolation, morphological characterization, and molecular identification by amplification of the gene encoding 16S rRNA. Of the 135 bacterial isolates, 121 of which were from M. alcicornis and 14 from P. dilatata, most belonged to the phyla Proteobacteria and Firmicutes, with the majority from the genera Vibrio and Bacillus. Coral metagenomic DNA was extracted and the gene encoding 16S rRNA was analyzed. The isolates were evaluated, in vitro, for antimicrobial activity against ATCC strains of Escherichia coli and Staphylococcus aureus, and 29 isolates from M. alcicornis showed activity against at least one of the bacteria evaluated. Using specific pairs of primers, 27 isolates showed amplification for at least one pair of primers designed for amplification of genes involved in the synthesis of non-ribosomal peptides (NRPs) and polyketides (PKs). However, only in some cases was a relationship detected between the isolates that showed antimicrobial activity in vitro and the isolates where amplification of genes involved in the synthesis of NRPs and PKs was observed.