Abstract
Following observations of survival of microbes and other life forms in deep subsurface environments it is necessary to understand their biological functioning under high pressure conditions. Key aspects of biochemical reactions and transport processes within cells are determined by the intracellular water dynamics. We studied water diffusion and rotational relaxation in live Shewanella oneidensis bacteria at pressures up to 500 MPa using quasi-elastic neutron scattering (QENS). The intracellular diffusion exhibits a significantly greater slowdown (by −10–30%) and an increase in rotational relaxation times (+10–40%) compared with water dynamics in the aqueous solutions used to resuspend the bacterial samples. Those results indicate both a pressure-induced viscosity increase and slowdown in ionic/macromolecular transport properties within the cells affecting the rates of metabolic and other biological processes. Our new data support emerging models for intracellular organisation with nanoscale water channels threading between macromolecular regions within a dynamically organized structure rather than a homogenous gel-like cytoplasm.
Highlights
Understanding the behavior of water inside cells is a long-standing problem in molecular biochemistry and cell biology[1,2,3,4,5,6,7,8]
Nuclear magnetic resonance (NMR) and quasi-elastic neutron scattering (QENS) studies at ambient pressure have demonstrated diffusional dynamics for intracellular water that are indistinguishable from bulk water or aqueous solutions over length scales extending from localized environments up to cellular dimensions30,31. 2H NMR spin relaxation data reveal ~15% water molecules that are strongly bound to internal surfaces, or buried within protein complexes[30]
After subtraction of the central Gaussian elastic line with its width determined by the instrumental resolution the QENS data were modelled by a narrow Lorentzian identified with translational diffusion, along with a broader second Lorentzian component from which rotational relaxation times could be extracted (Fig. 1 and Supplementary Figs 1–5)
Summary
Understanding the behavior of water inside cells is a long-standing problem in molecular biochemistry and cell biology[1,2,3,4,5,6,7,8]. Nuclear magnetic resonance (NMR) and quasi-elastic neutron scattering (QENS) studies at ambient pressure have demonstrated diffusional dynamics for intracellular water that are indistinguishable from bulk water or aqueous solutions over length scales extending from localized environments up to cellular dimensions. In a previous study we applied high-P QENS combined with H/D isotopic substitution of live organisms to investigate water dynamics in wild type (WT) Shewanella oneidensis at ambient and P = 200 MPa25. These results provided a first indication of diffusional slowdown occurring for intracellular water compared with aqueous hydrogenated or perdeuterated (Hb, Db) buffer solutions. As part of our study, we obtained data for pressure-resistant (PR) survivor populations that had been previously exposed to pressures of 500 (in a single compression step) and 750 MPa (via sequential intermediate treatments at 250 and 500 MPa, followed by resuscitation and re-compression) and compared the results with those for wild-type (WT) S. oneidensis samples[36,37] (Table 1)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
