Salt Sensitivity of Cells

Abstract

The first life form, a proto-cell, is believed to have evolved in the primitive sea. The sea nurtured early life supplying both inorganic and organic materials. However, it is not clear whether all the minerals positively supported proto-cells, although the mineral elements required by present-day cells are abundant in seawater. Geological evidence suggests that sea water accumulated upon the cooling of dense vapor in the atmosphere which derived from active volcanoes on the primitive earth. Therefore, we can assume that very little or no sodium chloride was present in primitive seawater when the proto-cells evolved. However, it is a fact that seawater currently contains on average, 3.5% sodium chloride. The increase in the sodium chloride concentration likely resulted from:(i) extraction from the solid earth, which has been estimated to contain 460 sodium atoms per 10,000 atoms of silicon (Gymer, 1973). (ii) evaporation of water into the atmosphere. Water evaporation from the surface of lakes is known to increase the sodium chloride concentration. For example, the salt concentration reaches saturation (about 35% at 20°C) in some area of the Dead Sea and Great Salt Lake. However, halophilic bacteria and certain other organisms flourish in this type of salt water.