Motivation

Synthetic biology faces our daily challenges and aims to develop new devices that provide solutions to every situation, every environment, and every problem that exists in the world. Many iGEM teams try to create such devices. Some teams try to collect heavy metal from sea water, drainage and so on, and other teams aim to detect some substrates through protein connections. Do they work most effectively under their applied environment? Insufficient of the concentration will be solved by adding sodium. But how about when salt concentrations are too high? You may think adding water is fine, but how will you dilute sea or sewage? Can you do that? Adding water changes other ion concentrations as well. Once devices that absorb salt are developed in certain surrounding containing strong salt concentration, we can greatly support various functions of other devices for sensing of substances in the environment and bioremediation. Therefore we aim to create a yeast desalination system in order to make iGEMers’ devices work appropriately under their applied situation.

Intracellular ionic strength influences various life phenomena

Life phenomena occur in an aqueous solution system. Therefore, various properties of aqueous solutions that depend on ions have various effects on life phenomenon. For example, electrostatic shielding and influence on hydration water by ions will have an effect on ionic bonds, hydrophobic effects, van der Waals’ forces. This will impact on protein-protein interactions and enzyme reactions by changing the stability of nucleic acid molecules and proteins. The asymmetric distribution of ions between the outside and inside of biological membrane enables rapid reaction response of the living body by generating membrane potential, and the change of water potential due to ion influences the mechanical environment of the cell by changing its osmotic pressure. For this reason, almost all reactions in vivo, including RNA folding, DNA double-stranded structure, protein-protein interactions, are greatly affected by salt concentration in solution. In other words, the created tools of iGEMers using biomolecules are greatly affected by the salt concentration in the environment. However, the iGEMer and their devices are developed to solve every possible problem in the world, so it is often unavoidable to face harsh circumstances or face the need to reduce Na + concentration. Our aim is to gather Na + from solution in biological process and to reduce salt concentration so that we could help these tools do their best performance.

Living organism has various transporters that selectively permeate Na +

Na + is one of the most abundant and functionally utilized ions in living organisms, and organisms have many Na + transporters to control and use. For example, Na + / K + - ATPase converts the energy of ATP into an electrochemical gradient through Na + transport, which establishes mass exchangeability of living organisms by becoming a driving force for co-transport and counter transport. Na + can be stopped due to maintained internal and external membrane concentration difference. It controls the membrane potential and further establishes the electrical function of the organism by acting as a source of the action potential by the voltage-dependent channel. In addition, Na + controls the resting membrane potential and works as a source of action potential to establish the electrical function of organisms. Thus, while Na + widely affects chemical reactions in vivo, it is an element widely and extensively present in the environment, such as seawater, and therefore often causes a problem. Some organisms, such as salt plants growing in the brackish water area, are known to have systems for protecting cells from such high concentrations of salt.