microbial fauna of deep sea vent crab species in comparison to shallow water counterparts (jack tyler)

Deep sea hydrothermal vents are majorly variable ecosystems with the fauna inhabiting the requiring highly niche adaptations. As well as the, symbiosis is rife, with bacteria aiding larger organisms to take up more oxygen or obtain the necessary nutrients that they need. Decapod crustaceans usually have a diverse range of bacteria associated with them.Epibiotic bacteria have been found on crabs before, however the gills and the intestines have been looked at very little.  

High-throughput sequencing of 16S rDNA allows a wider picture of the diversity of the microbial fauna present in a sample. For this study, Austinograea sp (deep sea vent), Eriocheir sinensis (fresh water but mates and spawns in saline water) and Portunus trituberculatus (salt water) were looked at to provide a wide picture of the diversity in the microbial communities within the gills of crabs.  

The highest and lowest diversity in bacterial communities were observed in the gill and intestines of Austinograea sp respectively. Through non-metric multidimensional scaling analysis, it was found that the bacterial community in Austiongraea sp was highly distinctive. Of the OUTs found, Leucothrix, Sulfurospirillum and Arcobacter may be involved in oxidizing reduced sulfur compounds and sulfur metabolism. Marinomonas and polaribacter are adapted to low temperature while Fusibacter and Psychrilyobacter may survive well under hypoxic conditions. Furthermore, bacteria commonly found in seawater were dominant in the gill, which is to be expected due to the fact that the gills filter water, but anaerobic bacteria showed high abundance in the intestines.  

The study shows that there is indeed a difference between the deep sea vent species and the two shallow water species when it came to microbiota. This is most likely due to the difference in habitat and food sources of the species. The deep sea species lives in an environment which is a lot harsher than that of the shallow water species, therefore, these novel species found are likely to aid the crab in surviving. whether that is uptake of nutrients in the gut or improved absorption of oxygen in the gills. Further to this the study provides evidence for tissue specific bacteria. 

Paper reviewed: 

Zhang, N., Song, C., Wang, M., Liu, Y., Hui, M., & Cui, Z. (2017). Diversity and characterization of bacteria associated with the deep-sea hydrothermal vent crab Austinograea sp. comparing with those of two shallow-water crabs by 16S ribosomal DNA analysis. PLOS ONE, 12(11), e0187842. doi:10.1371/journal.pone.0187842