Microbiota isolated from the sea cucumber (Isostichopus badionotus) native to Taganga Bay, Colombian Caribbean

Abstract

The bacterial and fungal communities associated to the skin and digestive tract of Isostichopus badionotus were identified in order to evaluate the antagonistic interactions among them. For this purpose, surface smears were made to the epidermis and digestive tract, and this smears were grown in bacteria – and fungi – specific culture media. The identification of microorganisms was performed considering colonial morphology on culture media and microscopic features. Also, biochemical tests through BBL Crystal® micromethods for Gram negative and Gram positive bacteria were applied to the purified bacterial colonies. The fungi were identified through microscopic observations and using taxonomic keys. The bacterial strains’ inhibitory activity was analyzed by the agar diffusion disk method.  Results showed a total of 42 isolated bacterial strains from which ten species were selected for taxonomic identification: Bacillus cereus, B. subtilis, Bacillus megaterium, Corynebacterium aquaticum, Proteus vulgaris, P. mirabilis, Enterobacter agglomerans, Serratia marcescens, Pseudomonas maltophilia, and Acinetobacter anitratus. Confrontation among these bacterial species did not show growth inhibitory activity. A total of 27 fungal strains were isolated, from which eight species were identified: Penicillium sp., Paecilomyces sp., Aspergillus sp., Aspergillus niger, A. flavus, Gliocladium sp., Cladosporium fulvum and C. herbarum. Fungal species showed inhibitory effects in dual confrontation tests. The identified species could correspond to the normal microbiota of the cucumber or to the microbiota associated to the water and/or the sediment, thus further studies are needed to confirm the obtained results.