Understanding the biochemical reactions and transport processes within cells, which are determined by the intracellular water pressure, could lead to a better understanding of how bacteria behave in different conditions. This experiment sheds light on how water management occurs inside prokaryotic organisms (organisms without a nucleus), and how dissolved ions, metabolites and macromolecular species would affect the mobility and transport properties of water in a macromolecular environment “crowded" by these molecules. Water mobility within cells determines metabolic function as well as other important biological processes.
Scientists from University College London in collaboration with other universities wanted to study biological functioning under high pressure conditions. Classic interpretations of prokaryotes (cells without a nucleus) present the intracellular cytoplasm as a gel-like medium containing dissolved ions and macromolecules such as lipids and proteins. However, the findings suggest a more structured internal environment, with cooperatively organised “superclustered" arrangements of proteins and macromolecular complexes, separated by channels enabling transport of the water-based electrolyte solution.
The scientists studied diffusion and rotational relaxation of water in live Shewanella oneidensis bacteria at pressures up to 500 MPa using quasi-elastic neutron scattering (QENS). Experiments were conducted at room temperature on three QENS spectrometers: the IRIS instrument at ISIS, IN6 at the ILL and TOFTOF at FRMII.
“Carefully designed experiments combining the unique technique of quasi-elastic neutron scattering with specialised sample environment equipment are allowing us to gain key insights into very complex entities that are cells. Moreover, it contributes to an understanding of intracellular organisation and metabolic rates at extreme conditions, significantly different to ambient" explains Victoria Garcia Sakai, beamline scientist on IRIS.
The results show that the intracellular water dynamics exhibit significantly greater slowdown compared with bulk water and aqueous electrolyte solutions of compositions comparable to those found in the cytoplasm. The pressure-induced viscosity increase and slowdown in ionic/macromolecular transport properties within the cells affect the rates of metabolic and other biological processes. The findings of this investigation lend further support to emerging models for intracellular organisation that could lead to new insights into biological functioning of organisms under ambient and high pressure conditions.
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Read the original paper at DOI 10.1038/s41598-019-44704-3.