Aluminum Tolerance Associated With High Intracellular Trehalose Levels In Saccharomyces Cerevisiae

Aluminum is the most abundant metal in the earth's crust, which covers about an area of 7% of the shell element all-up weight. Aluminum is the element that has high chemical values and its radius is small. It is often quite active in acid soil liquid and gives rise to poison the crop. It is a serious environmental toxicant and a primary factor limiting organisms' growth in acid soils.Yeast has been used to study the toxicity and tolerance of metal as a model bio-system. People find that yeast colonies display growing differences under aluminum stress or not, and the existence of Al³⁺ makes the yeast cells become more irregularly, and growing in clusters. At present, as for aluminum toxicity and tolerance mechanisms are still unknown, we are striving for answers to solve them.Trehalose is a nonreducing disaccharide in which the two glucose units are linked in an a ,a-1, 1-glycosidic linkage. This sugar is present in a variety of organisms, including bacteria, yeast, fungi, insects, invertebrates, and lower and higher plants. Large amounts of results have been shown that trehalose as stress protectant provides protection for biological molecules, it also acts as a stress protectant to counteract a variety of adverse environmental conditions.In this study, a mutant, designated as LKt, with high Al-tolerance was obtained from a Saccharomyce cerevisiae strain (LK) by mutagenesis with diethyl sulfate and U.V. LKt was able to grow on LPP plate containing 6 mM Al³⁺ while LK could only grow on LPP plate containing 2 mM Al³⁺. The relative growth rate of mutant LKt is significant higher than that of its parental strain LK upon various concentrations of Al³⁺.The results indicate that, under 800 μ M Al³⁺ stress, trehalose accumulation by LK and LKt increased by 5-7 folds, and that the mutant LKt could accumulate more trehalose than that of parental strain LK.Upon pro-exposure to mild heat shock or cells being in stationary phase, both trehalose accumulation and Al-tolerance of two strains were enhanced. These findingssuggested that the Al-tolerance of yeast strains may be in close relation to their trehalose accumulation. The difficult or easy level that the aluminum invaded inside the yeast cell relates with the yeast's enduring aluminum capacity. The yeast strain with strong Al-tolerance may possess the stronger ability to chelate aluminum and form a non-poisonous compound or to repel it outside the cell.