Characterization of the Bacterial Communities Inhabiting Tropical Propolis of Puerto Rico.

Propolis is a resinous material produced by honeybees from different plant sources and used in the hive as a building material and to protect the colony from parasites and pathogens. Despite its antimicrobial properties, recent studies showed that propolis hosts diverse microbial strains, some with great antimicrobial potential. In this study, the first description of the bacterial community of propolis produced by the gentle Africanized honeybee was reported. Propolis was sampled from hives of two different geographic areas of Puerto Rico (PR, USA), and the associated microbiota investigated by both cultivation and metataxonomic approaches. Metabarcoding analysis showed appreciable bacterial diversity in both areas and statistically significant dissimilarity in the taxa composition of the two areas, probably due to the different climatic conditions. Both metabarcoding and cultivation data revealed the presence of taxa already detected in other hive components and compatible with the bee's foraging environment. Isolated bacteria and propolis extracts showed antimicrobial activity against Gram-positive and Gram-negative bacterial tester strains. These results support the hypothesis that the propolis microbiota could contribute to propolis' antimicrobial properties.

Bacteria associated with toxic clonal cultures of the dinoflagellate Ostreopsis lenticularis.

The marine toxic dinoflagellate Ostreopsis lenticularis has been implicated as the major vector in ciguatera seafood poisoning on the southwest coast of Puerto Rico. Studies have demonstrated that associated bacteria play a role in the ciguatoxin production and that different clonal cultures of O. lenticularis harbor different culturable bacteria. In this study, more than 125 associated bacteria from two toxic clonal cultures of O. lenticularis (no. 302 and no. 303) were analyzed utilizing polymerase chain reaction amplification of the partial small subunit ribosomal DNA (rRNA), denaturing gradient gel electrophoresis, and DNA sequencing. Approximately 50% of total bacteria identified in both cultures were a single species belonging to the Cytophaga-Flavobacter-Bacteroides complex. This bacterium was also found in six new O. lenticularis clonal cultures established 10 years after the original cultures used in this study and absent from a clonal culture of a different dinoflagellate species. The data presented here indicate a persistent and apparently specific association of this bacterium with O. lenticularis, which makes it a candidate involved in ciguatoxin production.

Bacterial diversity associated with the Caribbean tunicate Ecteinascidia turbinata.

The Caribbean tunicate, Ecteinascidia turbinata produces the anti-cancer agent ET-743 that could well be a metabolite of an associated bacterial strain. This current study aims at the analysis of bacteria that are persistently and specifically associated with this invertebrate. Utilizing techniques such as denaturing gradient gel electrophoresis, DNA sequencing and phylogenetic analysis of bacteria from E. turbinata collected from different locations in the Caribbean Sea, we report here the identification of five possible persistently associated bacteria. Of these, only one organism, Candidatus Endoecteinascidia frumentensis, was found specifically associated to E. turbinata from the Caribbean and has also been found to be associated with E. turbinata from the Mediterranean. These experiments suggest that assessment of bacterial diversity associated with invertebrates from different geographical sites might be an effective way of identifying persistently and specifically associated bacteria.