Effects Of Food Sources On Bacteria Community In Gut Of Sea Urchin Diadema Setosum (Leske, 1778) Using Metagenomics Approaches

Abstract

16S rRNA metagenomics sequencing was applied for the study of bacterial communities in the gut of sea urchin, Diadema setosum from Mook Island, Trang province. Sea urchin samples were collected from three different food sources: around sand area, seagrass area and coral area for comparison between the bacterial community. In addition, bacterial community in the gut content of sea urchins were studied in two different conditions: the wild-caught and the starved sea urchin. The ambient sediment and seagrass leaves were also collected and analyzed. Both species richness and diversity indicies in the sediments were greater than the gut content and seagrass leaves samples. In the wild-caught sea urchins, Bacteroidetes, Proteobacteria and Firmicutes were the three most abundant phyla in all food sources. Surprisingly, there were no significant differences among bacterial community between the different food sources. In the starved condition, the proportion of bacterial composition was slightly changed. Proteobacteria tended to be increasing while Bacteroidetes was reduced. Bacterial communities between the gut content and the sediment samples were statistically significant different (p-value = 0.001). According to the results, bacteria detected in the gut are specific and differ from sediment and host diets. This may be result of the specific conditions of the intestine. It is also possible that resident microflora in the intestine can play the key role on their host nutrition. Moreover, sulfate-reducing bacteria (SRB), which involve sulfur cycle, were also detected in the present study. This group of bacteria might play a crucial role in sulfate metabolism in their host intestine.