Bacterial Diversity Associated with Millepora alcicornis, Phyllogorgia dilatata and Mussismilia harttii Collected from Two Distinct Corals Reefs on the Brazilian Coast

Corals can be considered holobiont organisms, since they have an important symbiotic relationship with microbial communities such as zooxanthellae, bacteria, Archaea, fungi and viruses. It is important to understand how those microbial communities influence the health of the corals and how environmental conditions could affect them. The present study aimed to describe the bacterial communities associated with three Brazilian coral species, Millepora alcicornis, Mussismilia harttii and Phyllogorgia dilatata, by a culture-independent method, using 16S rRNA gene sequencing. The corals were collected from two distinct coral reefs: Recife de Fora, in Bahia (BA) and Búzios, in Rio de Janeiro (RJ). The phylum Proteobacteria showed the highest relative abundance in most corals and sites. The bacterial compositions of these three corals from the two sample sites were very distinct from each other, not presenting similarities in coral species or related to sampling site. In M. alcicornes/RJ, the most abundant class was Gammaproteobacteria, order Piscirickettsiales, while the same species collected in BA showed unassigned Gammaproteobacteria, and Vibrionaceae was the second most abundant family. M. harttii/BA presented the most distinct bacterial phylum composition with 16 phyla (26% Proteobacteria, 16% Chloroflexi, 12% Acidobacteriota).