Abstract

The association between bacterial communities and eukaryotic organisms plays a fundamental role in maintaining the host’s state of health and its adaptation to the constantly changing environmental conditions.^1,2 To understand the mechanisms of interaction between the host and its bacterial communities, and the role of the latter within the marine ecosystems, it is necessary to know them in depth and to know their variations in response to endogenous and exogenous variables. This allows us to use the microbiota of marine mammals as a proxy for the health of their environment and as a marker to statistically measure any changes on the ecosystem within the One Health approach.

For the present project we collected samples of blow hole exhale (n=17), gastric juice (n=16), skin swabs (n=17), oral swabs (n=17), and fecal samples (n=16) from 17 bottlenose dolphins hosted in two different European facilities, Mediterraneo Marine Park (Malta) and the Oltremare (Italy). The aim was to characterize the microbial composition associated with the different body sites. We also collected samples of water from the tanks (n=4) coming from the two dolphinaria. Whilst one of the facilities has direct access to natural sea water, the other uses artificial sea water. However, both facilities use sodium hypochloride disinfection as part of their Life Support System (LSS).

Out of the 87 samples collected, sufficient total microbial DNA was extracted from 35 of them. This DNA was analyzed by sequencing the V3–V4 hypervariable region of the gene encoding for the 16S ribosomal RNA. The samples of gastric juice, oral and skin swabs did not provide sufficient material to proceed with analysis.

The results provided us with the general composition, in terms of bacterial phyla and families, of the characteristic microbiota associated to the different dolphin tissues and the water they live in. In the blow samples, the most abundant families were Flavobacteriaceae, Cardiobacteriales (as reported by Johnson³), Tissierellaceae, Porphyromonadaceae, Microbacteriaceae and Weeksellaceae. Bacterial families such as Peptostreptococcaceae, Clostridiaceae, Lactobacillaceae and Fusobacteriaceae, as previously reported,^4,5 mostly represented the intestinal microbiota. The water microbiota was most represented by Alphaproteobacteria. Comparing the level of biodiversity of the dolphin samples considered for this study, all the metrics used showed the greatest microbial diversity in the blow samples. Bacterial biodiversity of water samples was richer than in the fecal samples. These results provided us with a set of information to correlate the health of the animals and the environment also from a clinical perspective.

Acknowledgments

The authors wish to thank the animal staff from Oltremare and Mediterraneo Marine Park for their contribution.

*Presenting author

Literature Cited

1.  Lu L, Ting L, Yao Z, Chunhui C, Zhengwei F, e Yuanxiang J. 2019. Interaction between Microplastics and Microorganism as Well as Gut Microbiota: A Consideration on Environmental Animal and Human Health. Science of The Total Environment 667: 94–100.

2.  Xia J, Cuiyuan J, Zihong P, Liwei S, Zhengwei F, e Yuanxiang J. 2018. Chronic Exposure to Low Concentrations of Lead Induces Metabolic Disorder and Dysbiosis of the Gut Microbiota in Mice. Science of The Total Environment 631–632:439–48.

3.  Johnson R, Torralba M, Fair P, Bossart GD, Nelson KE, Morris PJ. 2009. Novel Diversity of Bacterial Communities Associated with Bottlenose Dolphin Upper Respiratory Tracts. Environmental Microbiology Reports 1,6:555–62.

4.  Soverini M, Quercia S, Biancani B, Furlati S, Turroni S, Biagi E, Consolandi C, et al. 2016. The Bottlenose Dolphin (Tursiops truncatus) Faecal Microbiota. FEMS Microbiology Ecology 92:4.

5.  Suzuki A, Segawa T, Sawa S, Nishitani C, Ueda K, Itou T, Asahina K, Suzuki M. 2019. Comparison of the Gut Microbiota of Captive Common Bottlenose Dolphins Tursiops truncatus in Three Aquaria. Journal of Applied Microbiology 126,1:3139.