Microbiomes of hadal fishes contain similar taxa, obligate symbionts, and known piezophiles across trench habitats

Hadal snailfishes are the deepest-living fishes in the ocean, inhabiting trenches from depths of ~6,000 to 8,000 m. While the microbial communities in trench environments have begun to be characterized, the microbes associated with hadal megafauna remain relatively unknown. Here, we describe the gut microbiomes of two hadal snailfishes, Pseudoliparis swirei (Mariana Trench) and Notoliparis kermadecensis (Kermadec Trench) using 16S rRNA gene amplicon sequencing. We contextualize these microbiomes with comparisons to the abyssal macrourid Coryphaenoides yaquinae and the continental shelf-dwelling snailfish Careproctus melanurus. The microbial communities of the hadal snailfishes were distinct from their shallower counterparts and were dominated by the same sequences related to the Mycoplasmataceae and Desulfovibrionaceae. These shared taxa indicate that symbiont lineages may have remained similar to the ancestral symbiont since their geographic separation or that they are dispersed between geographically distant trenches and subsequently colonize specific hosts. The abyssal and hadal fishes contained sequences related to known, cultured piezophiles, microbes that grow optimally under high hydrostatic pressure, including Psychromonas, Moritella, and Shewanella. These taxa are adept at colonizing nutrient-rich environments present in the deep ocean, such as on particles and in the guts of hosts, and we hypothesize they could make a dietary contribution to deep-sea fishes by degrading chitin and producing fatty acids. We characterize the gut microbiota within some of the deepest fishes to provide new insight into the diversity and distribution of host-associated microbial taxa and the potential of these animals, and the microbes they harbor, for understanding adaptation to deep-sea habitats.

Comfortable pressure feeling and clothing pressure on abdomen

PurposeThe present study obtained the topography of perceptible (a perfect-fit feeling) clothing pressures from the chest to groin, when a stretching material provided hoop tension to the body surface of participants. Furthermore, the allowable pressure level was examined for the abdomen, which is pressed by underclothes on a daily basis.Design/methodology/approachParticipants were nine women aged 21.3 ± 1.2 years. Each participant's perception of pressure while wearing the experimental band was obtained in a questionnaire using a visual analog scale. Clothing pressure was measured employing a hydrostatic pressure-balancing method as participants adjusted the band length themselves to achieve two conditions: a perfect-fit and tight-fit on the abdomen.FindingsThe range of comfortable clothing pressure tightening provided by a 2.5 cm-wide elastic band on the abdomen was 0–5.6 hPa for under the bust, waist and groin, and 4.4–9.3 hPa for the chest, lower waist and hips. A nerve plexus of the autonomic nervous system and arteries are distributed over the body surface of the former body parts, which were thus sensitive to tightening around the abdomen.Originality/valueThe topography of perceptible clothing pressure was obtained when stretching material provided hoop tension to the body surface of the participant. The results of a participant questionnaire agreed with clothing pressure obtained using a hydrostatic pressure-balancing method that has a short-time constant and sensitive resolution. Furthermore, allowable pressure levels were proposed.

High Hydrostatic Pressure–A Key Element to Investigate Molecular Dynamics in Biosystems

Temperature variations are often used to investigate molecular dynamics through neutron scattering in biosystems, as the required techniques are well-known. Hydrostatic pressure is much less applied due to technological difficulties. However, within the last decade, a reliable and suitable equipment has been developed at the Institut Laue Langevin, Grenoble, France, which is now available on different instruments. Here, an overview on its application in relation with elastic incoherent neutron scattering to study, for instance, the impact of transitions on atomic mobility in biological samples, is presented, as well as the conclusions that can be drawn therefrom.