Investigation of the microbial communities associated with the octocorals Erythropodium caribaeorum and Antillogorgia elisabethae, and identification of secondary metabolites produced by octocoral associated cultivated bacteria

Octocorals are important members of coral reef ecosystems. They are also a prolific source of bioactive secondary metabolites. Over the years there has been a growing body of evidence that suggests that secondary metabolites detected in marine macroorganisms, such as octocorals, are in fact biosynthesised by associated microorganisms. Therefore this research characterized the microbiomes associated with the octocorals Erythropodium caribaeorum and Antillogorgia elisabethae. In addition to the secondary metabolites produced by the cultivatable bacteria associated with these octocorals, as these octocorals are associated with the bioactive secondary metabolites desmethyleleutherobin and pseudopterosins, respectively.

Culture—independent studies utilizing 16S small subunit rRNA gene amplicon pyrosequencing were used to characterize the microbiome of E. caribaeorum collected from Florida, USA and San Salvador, The Bahamas at multiple time points. As well as the microbiome of A. elisabethae collected from San Salvador, The Bahamas, and the microbial communities associated with the dinoflagellates and larvae of this octocoral.

E. caribaeorum was found to have a very high microbial richness with an average Chaol estimated richness of 1464 ± 707 operational taxonomic units (OTUs) and average Shannon diversity index of 4.26 ± 1.65. The taxonomic class Gammaproteobacteria was a dominant member in all samples and the genus Endozoicomonas accounted for an average of 37.7% ± 30.0% of the total sequence reads. One Endozoicomonas sp. was found to be a stable member of all E. caribaeorum sequence libraries regardless of location or time of collection and accounted for 30.1% of all sequence reads.