Prolonged Saturation Exposure Alters Human Gut Microbiota: A Case Report

PURPOSE Prolonged saturation exposure induces digestive disorders, affecting health related life quality of divers. The diversity of the gut microbiota has been associated with various health parameters. Therefore, we hypothesized that prolonged saturation diving would result intestinal microbiota dysbiosis in human. In this case report, the feces of elite divers were collected after a saturation diving mission to examine the gut microbiome. METHOD Two elite male divers were recruited for this study. This study was approved by the Research Ethics Committee of Naval Medical Research Institute. Exclusion criteria included having antibiotic treatment within previous month, drinking alcoholic within one week, or suffering from any gastrointestinal or immunological disease. During the entire experiment, divers were provided the same diet and living condition. Divers were compressed to depth of 300 m with helium-oxygen, and held for 24 hours to saturation. During the saturation stay, they made an excursion diving to 330 m undersea, then surfaced after a 15-day decompression. Their feces were collected within 24 hours before compression (0–1, 0–2), immediately (1–1, 1–2) and a one-month recovery after decompression (2–1, 2–2). The fecal microbial DNA was extracted and sequenced on an Illumina MiSeq platform. Principal coordinates analysis was applied to detect the differences of gut microbiota compositions of all samples. The similarity of all gut microbiota compositions were analyzed, and presented in the Heatmap. RESULTS Pre-mission (one week before mission) physical examination was applied. Diver 1: age 26, 56 kg, BMI 20.5; Diver 2: age 30, 74 kg, BMI 23.9. The gut microbiota composition and diversity baseline of two divers were no different. Shown in Venn diagram of diver 1, 49 genera were shared by samples of all three periods, while 6 in 0-1, 13 in 1-1 and 18 in 2-1 were unique. And in diver 2, 49 genera were found in samples of all periods, while 7 in 0-2, 9 in 1-2 and 12 in 2-2 were not overlapped. The relative abundances of gut flora in each sample were presented in phylum and genus levels. The major alteration of gut microbiota occurred in phylum of Firmicutes. The relative abundances of Terrisporobacter genus, in which some species were related to infections, turned from 0.047±0.032% before compression, to 4.293±3.381% after decompression, then drop to 0.077±0.052. On the contrary, the genus of Ruminococcaceae, which have several beneficial bacteria, took 0.496±0.087% of microflora before compression, decreased to 0.015±0.009%, and increased to 0.747±0.005% after recovery. Significant changes of some nutrients and energy metabolism related microbes were found in both saturation exposure and recovery. Despite the variation of the microbiota relative abundances, 0-2 and 1-2, as well as 2-1 and 2-2, showed notable similarity. Meanwhile, after living together for nearly two months, the mircrobiota compositions tended to be similar. CONCLUSION In our study, saturation exposure or recovery remarkably influenced divers' gut flora. As the change pattern of some pathogens, divers may be vulnerable to infectious diseases or digestive disorders during saturation exposure. Compositions of nutrients and energy metabolism related microbes were changed notably, but presented large interpersonal variations. Analysis of related physiological indices and further studies are needed in order to illustrate the effects of saturation exposure on divers' microbiota and health. Support or Funding Information Found: PLA Youth Training Project for Medical Science (16QNP022), Major Logistics Projects of PLA ( AHJ11J004, AWS16J033), National Natural Science Foundation of China (31471135, 31701040), Shanghai Sailing Program (17YF1418000) and Chenguang Program (16CG57). This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.