Shifts in the Oral Microbiota During a Four-Week Commercial Saturation Dive to 200 Meters

During commercial saturation diving, divers live and work under hyperbaric and hyperoxic conditions. The myriads of bacteria that live in and on the human body must adjust to the resultant hyperbaric stress. In this study, we examined the shifts in bacterial content in the oral cavity of saturation divers, using a metagenomic approach to determine the diversity in the composition of bacterial phyla and genera in saliva from 23 male divers before, during, and immediately after 4 weeks of commercial heliox saturation diving to a working depth of circa 200 m. We found that the bacterial diversity fell during saturation, and there was a change in bacterial composition; with a decrease at the phylum level of obligate anaerobe Fusobacteria, and an increase of the relative abundance of Actinobacteria and Proteobacteria. At the genus level, Fusobacterium, Leptotrichia, Oribacterium, and Veillonella decreased, whereas Neisseria and Rothia increased. However, at the end of the decompression, both the diversity and composition of the microbiota returned to pre-dive values. The results indicate that the hyperoxic conditions during saturation may suppress the activity of anaerobes, leaving a niche for other bacteria to fill. The transient nature of the change could imply that hyperbaric heliox saturation has no lasting effect on the oral microbiota, but it is unknown whether or how a shift in oral bacterial diversity and abundance during saturation might impact the divers’ health or well-being.

IMPACT OF HYPERBARIC STRESS ON LIPID COMPOSITION OF BLOOD PLASMA AND PHYSIOLOGICAL-BIOCHEMICAL CHARACTERISTICS OF ERYTHROCYTES IN DIVERS: PREVENTION OF VIOLATIONS BY VEGETABLE POLYPHENOLS

There was studied lipid composition of blood plasma and erythrocyte membranes, physiological characteristics of erythrocytes in divers, exposed to extreme factors of the hyperbaric environment in the process of the occupational activity. There was observed a group of 10 male divers from 25 to 30 years of age, whose work is associated with the systematic implementation of submarine dives at medium and large depths (20-60 m) using compressed air for breathing. The influence of hyperbaric stress was shown to be accompanied by the change in a ratio of fatty acids in the total lipids of blood plasma and erythrocyte membranes. In total lipids of blood plasma and erythrocyte membranes the number of all kinds of saturated fatty acids (myristic acid, palmitic acid, stearic acid), the monounsaturated fatty acids (palmitoleic acid) was increased and an amount of polyunsaturated fatty acids of n-6 family (arachidonic acid) and n-3 (eicosapentaenoic acid) was reduced, which caused a change in physicochemical properties of erythrocytes, permeability, and lability. The increase in the amount of cholesterol in the erythrocyte membranes correlates with its elevation in blood plasma. There was an increase in the volume of erythrocytes by 5% and diameter by 13%, due to the inclusion of cholesterol in the membrane. It was recorded a shift in the threshold of hemolysis start at 0.50 ± 0.02% NaCl and its completion at 0.40 ± 0.01% NaCI. Preventive administration of the Kalifen food supplement for two months before the dive would help to remove metabolic disorders caused by the hyperbaric factors.