Assessment of bacterial communities in skin ulceration in cultured sea cucumber Apostichopus japonicus (Selenka)

To determine changes in bacterial composition in skin ulcerations in farmed sea cucumber Apostichopus japonicus, full-length 16S rRNA gene sequencing of different skin samples of A. japonicus was performed on a Pacific Biosciences (PacBio) RS platform. The fact that one of them varies in bacterial diversity than the other two may suggest different stage of skin ulceration, but the answer is inconclusive due to inefficiency in size of sampling pool. After comparing them with three skin samples from three healthy sea cucumbers, respectively, the majority of the results were distinguishable at the species level. The bacterial composition, which increased in diversity during the possible early stage of skin ulceration, exhibited a decrease in diversity at possible advanced stages, except for the predominant Saccharicrinis carchari (846.85 ± 5.75‰). This work may have the first clue implicating Ornithinibacillus contaminans as a potential causative pathogen of skin ulcerations in A. japonicus.