Diversidade de bactérias não-cultiváveis associadas ao zoantídeo Palythoa caribaeorum

Abstract

Much of the rich genetic and marine metabolic diversity not yet exploited is found in coral reefs, which also support several microorganisms that play an important role in host health, providing a source of food and occupying specific niches, forming a complex community currently called holobiont coral. The species Palythoa caribaeorum is a zooxantellated zoanthid identified as a key species in the Brazilian Northeast reefs, and that until then did not have its bacterial community characterized. Our work aimed at describing the taxonomic inventory of bacteria associated with coral P. caribaeorum through the partial pyrosequencing of the 16S rDNA gene. The collections were carried out in March of 2015, in two places: coral reef of Ponta Verde and sandstone reef of Sereia, both in Maceió - AL. Fragments from six different healthy colonies of P. caribaeorum had their total genomic DNA extracted and sequenced through a pyrosequencer. The sequences obtained were analyzed according to the protocol proposed by the Brazilian Microbiome Project. A total of 26,166 sequences were obtained, reduced to 8,988 after quality control, generating a total of 459 OTU's with 97% identity. At all taxonomic levels the diversity found was greater in the Sereia reef, as well as the number of sequences classified as "uncultured". In total, 21 phyla were found, being 10 exclusive of the reef of the Sereia and only one of Ponta Verde. In general, Proteobacteria (average of 57.4%) was the most abundant phylum, whereas the representativity of other predominant groups, such as Actinobacteria, Acidobacteria and Chloroflexi, was quite variable among the samples, corroborating previous studies with other species of Palythoa. In addition, diversity analyzes have shown that in the Sereia reef, the microbiota associated with coral was more similar and diverse than that found in the microbiota of the Ponta Verde corals, which showed to be undergoing changes in composition, presenting about 25% of the sequences classified as belonging to genera potentially pathogenic of humans, such as Streptococcus, Staphylococcus and Propionibacterium, probably introduced by the sewage discharge that occurs in region. Our results corroborate previous work that also found variations, mainly in the abundance of the groups shared between the coral microbiota collected from an unconfined environment when compared to an environment affected by sewage discharge. Our results extend to zoanthids what has already been said about scleractin corals, which different species of healthy corals have distinct and apparently specific bacterial communities under normal conditions. We conclude that the species P. caribaeorum has a rich and diverse microbial community associated, having variation between the two points collected, possibly caused by anthropic factors.