A potential contribution of the less negatively charged cell wall to the high aluminum tolerance of Rhodotorula taiwanensis RS1

Abstract

Rhodotorula taiwanensis RS1 (Rt) is a high-aluminum (Al)-tolerant yeast that can survive Al at concentrations up to 200 mM. In this study, we compared Rt with an Al-sensitive congeneric strain, R. mucilaginosa AKU 4812 (Rm) and Al sensitive mutant 1 (alsm1) of Rt, to explore the Al tolerance mechanisms of Rt. The growth of Rm was completely inhibited by 1 mM Al, but that of Rt was not inhibited until Al concentration was more than 70 mM. The growth of alsm1 was inhibited much more by 70 mM and 100 mM Al than that of Rt. Compared with Rm cells, Rt cells accumulated less Al in the cell wall and cytoplasm. A time-course analysis showed that Al was absorbed by Rm cells much more rapidly than by Rt cells when exposed to the same Al concentration. Meanwhile, the Al content of alsm1 was higher than that of Rt. Although the cell wall of Rt was thicker than that of alsm1 and Rm under control and 0.1 mM Al, that of Rt was thinner than that of alsm1 under 70 mM Al despite that their cell walls were thickened. The alcian blue adsorption was lower and cell wall zeta-potential was higher in Rt and alsm1 than in Rm, indicating a less negative charge of cell wall of Rt and alsm1 than that of Rm. Taken together, the less negatively charged cell wall of Rt may restrict the adsorption of cationic Al in cells, potentially contributing to its high Al tolerance. Copyright © 2016 John Wiley & Sons, Ltd.

Isolation of Aluminum-Tolerant and -Absorbing Yeast

“…These two strains were thus selected as AlCl 3 -tolerant yeast strains with higher Al absorbability and named Alt-OF2 and Alt-OF5, respectively, even though intracellular location of Al absorption in these strains remains unknown. Our preliminary experiments indicate the possibility that the Al concentration at the cell wall is lower than that of the total Al concentration, using the method of Hu et al (2016) .…”

“…Rhodotorula sp. is a highly Al-tolerant yeast with high surface adsorbability (Hu et al, 2016) . However, it is better to use uncolored (near white) strains of Al-absorbing yeast than red strains in solubilized foods or beverages, because staining materials from colored yeast potentially decrease food quality.…”

Isolation, identification of an aluminum-tolerant strain and its tolerance characteristics

“…These aluminum-tolerant bacteria include Acidocella aluminiidurans, Flavobacterium sp., Pseudomonas fluorescens, Arthrobacter sp., Burkholderia sp., and Bacillus cereus B5 [3][4][5][6][7][8][9]. The reported aluminum-tolerant fungi include Saccharomyces cerevisiae, Lipomyces, Rhodotorula taiwanensis RS1 [9][10][11]. At present, most of the obtained fungi are yeasts.…”