Response of bacterial community in sea cucumber Apostichopus japonicus intestine, surrounding water and sediment subjected to high-temperature stress

Abstract

During the anomalously hot summer of 2018, the water temperature in a sea cucumber culture pond reached 28–33 °C. As a result, many sea cucumbers died from the high temperature, causing huge economic losses. Currently, changes in the bacterial community of the sea cucumber culture pond ecosystem during high temperature remain largely unknown. In this study, we investigated the effects of high temperature on the community composition and function of the sea cucumber culture pond ecosystem using high-throughput sequencing. The results showed that bacterial communities in the Apostichopus japonicus intestine, surrounding water and sediment responded quickly to high temperature, as indicated by an obvious succession process of the dominant and specific bacterial community. At high temperature, the richness and diversity of the bacterial community in the water and sediment decreased significantly (P < 0.05). The richness of the bacterial community in the A. japonicus intestine was significantly increased, and several potential pathogens (Staphylococcus, Vibrio and Pseudomonas) changed in terms of their dominance, increasing the risk of disease in A. japonicus. The predictive functional profiling based on the Clusters of Orthologous Groups (COGs) database showed that the restraint of water, sediment, and the intestine bacterial community under high temperature were characterized mainly by the weakening of metabolism, environmental information processing and cellular processes, and post-translational modification, protein turnover, chaperones. The bacterial community may adapt to a high temperature by enhancing information storage and processing, amino acid transport and metabolism, and carbohydrate transport and metabolism. In the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database analysis, 64 KEGG pathways showed significant differences, which could be classified into six KEGG A classes and 23 KEGG B classes. The main differences in the KEGG pathways of the bacterial community in water, sediment, and A. japonicus intestine at high temperature were reflected in metabolism, cell motility, and environmental information processing. By changing its structure and group behavior, the bacterial community might be inhibited or adapted to the high temperature with both attributes dependent on changes in functional proteins and metabolic pathways. The findings of this study provide guidance for maintaining a healthy aquaculture environment.