Heavy metal pollution has become a great concern due to its adverse effects on the ecological system and human health. Major increase in heavy metal are caused by intensive human activities and economic development. For this reason, when extracting salts from mineral water that are necessary to produce other products such as food supplements, cosmetics, and laboratory reagents, pollutants are also extracted.
Haloarchaea are unique microorganisms resistant to environmental and osmotic stresses and thrive in their habitats despite extreme salinities. The results of previous studies have shown that the concentration of calcium and magnesium ions in the medium affects the stability of the membranes of Haloarcula hispanica and their energetic activity related to the efficiency of electron transport through the repiration chain in the plasma membrane [1]. The knowledge of microorganisms living in hypersaline environments is still limited and further investigation is needed to determine energy transformation methods and environmental adaptation conditions. To extend the results of these studies, experiments with high concentrations of Ca2+ and Mg2+ salts in archaeal environments are needed. Due to particularly high concentrations of Ca2+ and Mg2+ salts in the medium, the concentrations of pollutants, especially heavy metal ions, also increase, cause morphological changes in archaea and inhibit their reproduction. This forces archaea as bioindicators in the studies of purity of Ca2+ and Mg2+ salts isolated from natural resourses, i.e., mineral waters.
Monitoring the dissolved oxygen concentration changes in the H. hispanica incubation medium, it is possible to follow the respiratory activity of cells, register the effect of substances – components of the medium. Observing the decrease of dissoved oxygen concentration in medium of archaea growing in light, it is not easy to assay the ion transport activity, as light activates light-driven proton pumps, which cause reduction of archaea respiration. This effect was interpreted as the result of competition between two energy yielding systems: the light-driven rhodopsin proton pumps and the respiratory chain. During the dissolved oxygen measurements, it was found that additional factors, in parallel to light, also affect the archaea's oxygen uptake such as cell preparation for measurements; stock suspension storage conditions; or medium for measurement. Based on H. hispanica respiration measurements, a new method for biotesting of calcium and magnesium salts was developed.